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Travelor
01-01-2008, 06:34 AM
I am a novice when it comes to reading the wind and coping with it, but I "think' I am able to read ballistic tables.

The fellow shooters at the line and on the Long Range Shooting Forum keep telling me that the 223 will not hold up to the wind as well as a 308 - they refer to bullet weights and field experience. They say that the 223 is MUCH HARDER to shoot well at 1000 yards due to greater affects caused by the wind on the lighter bullet.

Running the ballistic tables and cross checking velocities with a chronograph, I see that I can get a 223 Rem with a Berger 75 grain VLD to out perform a 308 with a Sierra 155grain MK's as far as wind drift is concerned. Also, I know from personal experience that my wife's 6mmBR with a 107 SMK requires less wind correction than my 308 with a 155 SMK when we shoot side by side in the same match as we compare wind settings and results.

Am I missing something or is this just an old range myth?

mikecr
01-01-2008, 10:11 AM
No you've got it. Simple BC

Cheechako
01-01-2008, 11:36 AM
. . .The fellow shooters at the line and on the Long Range Shooting Forum . . .

Are wrong! Old wives tales and myths are hard to bust.

Ray

Asa Yam
01-01-2008, 01:58 PM
Ray,

That's because we're smarter, and know when to ignore benchresters! :D

Seriously, one of the issues we're up against is the BCs themselves. My experience says the published values aren't correct, but others disagree. On top of that, the most common model (G1) fails to adequately describe the performance of boattailed hollowpoint projectiles. Not surprising that predicted vs actual results fails at long range.

Solutions:
Generate your own ballistic tables. This means measuring muzzle and target velocities, or times of flight.
Use a more appropriate ballistic model. G5 or G7 work much better for boattail match bullets, especially if velocity near the target approaches the transsonic range (Mach 0.8 to 1.2). G5 is more appropriate for shorter radius ogive boattailed projectiles (i.e., Sierra 155), while G7 better models the behavior of low drag projectile designs (i.e., VLD bullets, and long ogive projectiles such as .224" 80 grain and 107 grain 6mm Sierras).
Accept the difference. Do a better job reading the wind, and outshoot your opponents. In other words, become a true rifleman.

Louis Boyd
01-01-2008, 02:49 PM
No you've got it. Simple BC

Simple BC combined with muzzle velocity does determine both wind deflection and total drop. However, there is more to accuracy than that. All bullets have some level of instability even if they are perfectly made. Some computer programs can roughly predict the level of that stability but none can predict the trejectory varitions caused by it to the extent they can predict shot to shot point of impact or even group sizes. This is why short range benchrest shooters (with "short range" sometimes including 1000 yards) don't use the highest BC's or the highest velocities possible. That simply doesn't give the best accuracy unless the wind is so unpredictable that it dominate all other error sources.

Both the 308 and the 223 have a relatively low combination of muzzle velocity and BC (not a simple multiplication) compared to the top cartridges used for 1000 yard shooting but they are fairly competive with each other with proper bullet choice.

While Mythbusters is a fun show sometimes their experiments differ enough from the myths they're trying to bust that their conclusion (in my opinion) are wrong. A good example was how far you have to be underwater to be safe from a rifle bullet fired from above including a .50 BMG. They were definitely not using the .50 BMG ammo which would give the longest underwater range. I also question their conclusions about bullets fired into the air being deadly or not. Certainly dropping bullets from a balloon wasn't a valid experiment.

Big Al
01-01-2008, 04:07 PM
I guess it all depends on how you figure BC. Using Serra method, that has velocity as part of the component. Which would mean that the BC is ever changing with distance as velocity falls off.

Anybody bother to look-up the origin of BC and see the relationship between black powder and to today's use of the term?

mikecr
01-01-2008, 06:00 PM
I'll try again..
Regardless of cal, if you're competing at 1K with lower BC bullets(albeit accurate -up close), you've likely lost to the field before taking a shot.
This is because wind is the dominant factor at distance, and not accuracy. If it were the other way, the 6PPC would rule there as well..
No
Nearly everyone on that line is using heaviest per cal bullets. Some enduring way more recoil than they should to ensure this condition.
You should be grateful for any BC standard, and you should not deny the importance of it.
Especially, if you're one of the 99% shooting heaviest per cal...

Mark S
01-01-2008, 09:44 PM
Myself and several others on this board shoot a local match each summer, that is broken into 3 classes. They are 223, Factory 30 cal, and anything,
factory30 meaning 308 & 30/06 in factory action and twist, ANYTHING meaning any gun 300 win mag & lower.

At every match the 223 shooters post higher scores than Factory 30. This has been a regular discussion, as most are loading 80gr Berger's out of 7-8 twist barells,& the 30's are mostly 178 SMK's out of 10 twist tubes.

Course of fire is 600,800,900,&1K, 5 rnds @ each, with no sighters. The score is 1 MOA= 10pts, 2 MOA= 5 pts, not as easy as most think,but the 223 pulls 10-12% higher scores.

I don't know if it help's you out, but it's what I have seen here over the last four years.


Mark

milanuk
01-02-2008, 10:46 AM
Mark,

It'd be interesting to see a break-down of the scores vs. caliber vs. range for that match.

I could easily see a .223 cleaning up at 600. I could even see it at 800. We don't see a lot of .223 in F-Class around here, but I have to wonder if they get far enough ahead and stay there.

I know myself and some others have toyed with the idea of a second gun in .223 rem for closer yard lines (600yds and in) since rule 9.1 (switching rifles) continues to get 'ignored' in F-Class. Figure if they're going to flaunt the rule (at least the Nationals specifically write it in the match bulletin that its is being ignored) might as well play along.

Monte

Darkker
01-05-2008, 12:49 PM
Well the one thing that strikes me as "funny" here is that no one tackled the obvious bullet problem.
You aren't compareing apples to apples. The 75gr in 223 I have no problem with, But the 155gr in 30 IS NOT a 1000 yard bullet! Unless you have a "holy-crap" house load, 168gr isn't a 1000 yard bullet. The 168's go sub-sonic somewhere after 900.

You need to compare the 175-178's to be apples to apples.

milanuk
01-05-2008, 01:09 PM
Well the one thing that strikes me as "funny" here is that no one tackled the obvious bullet problem.
You aren't compareing apples to apples. The 75gr in 223 I have no problem with, But the 155gr in 30 IS NOT a 1000 yard bullet!



Excuse me?!?

Pretty sure they work just fine to 1k, and a whole hell of a lot of people use them as such in Palma, TR, and F/TR

Generally speaking, the reason for comparing 75/80gr bullets to the 155s is because a) in some parts of the world (Canada for one), F/TR is limited to 81 grains or less in .224 cal, and 155gr or less in .30 cal, and b) the factory advertised BCs are comparable. The Berger 75 VLD lists at .447, and hte 80gr VLD at .471; by way of comparison, the 155gr BT lists at .453 (very close to the 155gr SMK and Nosler bullets, fwiw) and the 155gr VLD at .472. And the loads are going at comparable velocities (2900-3000+). So tell me again how we're not comparing 'apples to apples'?

YMMV,

Monte

AJ Peacock
01-05-2008, 02:36 PM
I am a novice when it comes to reading the wind and coping with it, but I "think' I am able to read ballistic tables.

The fellow shooters at the line and on the Long Range Shooting Forum keep telling me that the 223 will not hold up to the wind as well as a 308 - they refer to bullet weights and field experience. They say that the 223 is MUCH HARDER to shoot well at 1000 yards due to greater affects caused by the wind on the lighter bullet....


Please post a reference to the thread from the LR forum.

In reading some ballistics tables.

.223 at 2900fps w/ 80gr Berger has 8.75moa wind drift @1000yds (10mph 90 degree to line of flight)

.308 at 2900fps w/ 155gr SMK/palma has 9.75 moa drift@1000yds (10mph 90 degree)

.308 at 2500fps w/ 210 berger vld has 7.50moa drift@1000yds (10mph 90 degree)

Kinda depends what you are comparing. Makes sense when you compare heavy for caliber bullets in both chamberings.

Thanks,
AJ

Cabrera
01-05-2008, 06:05 PM
-----Just edited the post, with the hope of making it more understandable-----

I have never seen a treatment on wind deflection with transients conditions considered. The approach we all use is considered "static", in which the bullet drifts the whole duration of its retardance time.
No consideration is given that there is always some "slippage" at the very start/stop (transients) due to inertia, and this inertia is directly proportional to weight.
Let's consider this condition; a total reversal of wind conditions at half way down range. A shooter using same BC with light bullets, will read the condition closer to him, compensate for it, and get a wrong shot, because the wind downrage was capable to more than compensate the initial/closer drift, and maybe even make a reversal on total drift. Results: the shooter misread the condition and missed the shot.
In those same conditions, a shooter using same BC, but with heavier bullets, his shot placement was not as bad, because the downrange conditions was not able to outdo the inertial (kinetic) energy created by the first half of the drift, causing the bullet to impact in a more predictable manner, most likely NOT with a total reversal.
Taking the light bullet case/with same BC to its limit, an infinitesimally small/light bullet (zero+ grain but with same BC as a much heavier and practical one), will drift instantaneously to changes in wind, making it close to impossible to correct (dope) in any long range scenario. This case I think shows why heavier bullets are more "wind readable" in practice. All this is happening with the same BC, with the same muzzle velocity, with accordingly same ballistics.
All in all, I am a total believer of heavier is better for longer range. The problem is in having a heavier bullet with the same accuracy. To do same BC and heavier, it calls for a larger caliber, and handling the extra recoil becomes the issue.

Good shooting,

George

Darkker
01-06-2008, 12:08 AM
2900-3000+ and you don't call that a hot load in a specific gun, for a 308?!
As I said, average load for each, not holy crap!
If you stay in the average range the 155's will be going sub-sonic before the 1,000yard mark.
I'm not saying it Can't be done. I'm saying the heavier bullets are easier to get it done.

IF, as it has been pointed out since the post, you are comparing apples to apples; you must compare "heavy for caliber" against "heavy for caliber" bullets.
Not heavy versus light.
Next time you go towards the Tri-Cities Monte, you bring your loads, I'll buy lunch, and we'll have a good time throwing lead.

milanuk
01-06-2008, 12:39 AM
Nope. No a hot load at all, and it's one thats been in use for years (probably decades) in Palma/TR. Long (30-34") premium match barrels with tight chambers, short throats and slow twists (1-12, 1-13, etc.) help, but I've also punted 155s out at 2890-2930fps from 26" factory Savage and Remington barrels. My factory 12 F/TR tube did 2960 w/ a Berger 155gr VLD.

Honestly, it really is a 'standard' load. If I'm not mistaken, the U.S. Palma team specs 2950-2975 as the 'target' velocity for team members to load their ammo to. The 155 really sings in that region, and it simplifies the wind calls for the coaches to have everybody shooting nearly the same load. Ask any Palma or TR shooter how fast their 155 loads are going: The slowest I've heard of is the load the Brits used @ the World LR championships this past summer - 2860fps w/ a Berger 155 BT.

Like I said, the standard Palma .308 load is a 155 @ 2900-3000fps, and since the bullets have comparable BCs, the .223 loads get compared against it. I've heard (and sadly, heeded) the same 'wives tales' mentioned by the OP. Generally I've found that by the time the gents on the line make it to High Master w/ a sling, they've tried enough stuff that I tend to take it seriously but usually I follow the 'trust but verify' creed. I certainly wouldn't mind shooting a .223 if it holds up in switchy winds - less recoil almost always allows a shooter to perform better.

There's a Palma/65 match for Prone/F-Class down @ Rattlesnake on February 23rd... 15rds each @ 800/900/1000, plus another 20 @ 1000yds. See ya there.

Who do I ask for again? ;)



Monte

milanuk
01-06-2008, 04:07 AM
For those interested in what has been said on the matter elsewhere (specifically the thread A.J. was wondering about)...

http://www.long-range.com/forums/index.php?s=&showtopic=8905&view=findpost&p=62991

Travelor
01-06-2008, 06:25 AM
I knew soon or later someone would find this same posted question by me with replies on the Long Range Target Shooting Forum. I posted here as I believe this Forum is more analytical than the other one when it comes to theory meeting the target.

The posters on LR Shooting Forum were reporting on field observations rather than ballistic tables which is undeniable the best way to analyze as long as everything else is equal, HOWEVER, one wonders if this field observation is based upon similar level shooters or not. My very limited observations are that 223's are shot more by entry level shooters that 308's. Remember I said very limited observations.

My thoughts are that to see if there really is a difference would be to shoot equal qualitiy guns in the two calibers from a bench by the SAME High Master shooter on the same day and see how the scores/groups fall out.

Thanks for the thoughts and insights. Learning every day.

George

Asa Yam
01-06-2008, 03:34 PM
I knew soon or later someone would find this same posted question by me with replies on the Long Range Target Shooting Forum. I posted here as I believe this Forum is more analytical than the other one when it comes to theory meeting the target.
Horsefeathers. Many of the same people there are here as well. That pool of shooters includes retired and practicing engineers, race car mechanics, pilots, and even farmers. All of whom are very much interested in how theory translates to the real world - and often, how well the theory applies. Some of the posters in your LRTS thread are also some of the best in the world in the prone shooting game - lots of experience.


The posters on LR Shooting Forum were reporting on field observations rather than ballistic tables which is undeniable the best way to analyze as long as everything else is equal, HOWEVER, one wonders if this field observation is based upon similar level shooters or not. My very limited observations are that 223's are shot more by entry level shooters that 308's. Remember I said very limited observations.

My thoughts are that to see if there really is a difference would be to shoot equal qualitiy guns in the two calibers from a bench by the SAME High Master shooter on the same day and see how the scores/groups fall out.

Heretical Statement: Shooting from the bench isn't the only way to test how well a rifle and ammo shoot. Quite a few accomplished long range shooters don't. When you're talking about prone and F-Class shooting, remember this: It's the archer that usually makes the biggest difference, not the arrow. A 1/4 MOA rifle in the hands of a 1.5 MOA holder (RSS = 1.52) simply won't perform as well as a 1 MOA rifle in the hands of a 1 MOA holder (RSS = 1.41 MOA).

There is also an intangible factor that shooting from a bench probably won't give you. I know of at least one HM who gave up shooting .308s and switched to .223s for the long range prone game. Not because of a difference in group size, but because the cumulative effects of less recoil made it easier to shoot the .223 well over several days. (Prone matches usually consist of 60+ shots/day.)

DISCLAIMER: I am an Admin at Long-Range.com, though derive no financial or material benefits from doing so.

pbike
01-06-2008, 03:44 PM
Darkker....

155 at 2950 is not a holy crap load... It is a standard when shooting Palma, the key is Palma rifles have 30 inch barrels. This is easily achievable with Lapua Brass, Sierra 155 bullets, Federal GM 210 M primers and, a dose of Varget.

Paul

Big Al
01-10-2008, 01:58 AM
While Mythbusters is a fun show sometimes their experiments differ enough from the myths they're trying to bust that their conclusion (in my opinion) are wrong. A good example was how far you have to be underwater to be safe from a rifle bullet fired from above including a .50 BMG. They were definitely not using the .50 BMG ammo which would give the longest underwater range. I also question their conclusions about bullets fired into the air being deadly or not. Certainly dropping bullets from a balloon wasn't a valid experiment.

My Son saw this programme the other day and asked me about it and bullets in the water. He had heard me tell stories of what happened to the NVA and Vietcong when they would dive in the canals, trying to escape us overhead shooting at them with M-60's from helo gunships. I see in my minds eye the results often, what goes down must come up. When people are in a panic, they use up O2 much faster. These people were in a panic, the canals were no deeper than 12 ft. not once do I remember any man that jumped into the water surviving, you can't tell from the surface how deep a man is under the surface. Every crew member knew that a man under the water was a dead man. This was shooting one in five, ball, tracer 7.62 NATO ammo. That friends is the real world of bullets in the water, not Hollywood's version.

mysticplayer
01-10-2008, 03:03 PM
Been shooting the 308 LR for a number of years and have now started playing with the 223 because of this very same debate.

What I have found is that the BARREL determines my outcome.

I have built several 308's where their best accuracy with the 155's was 2800 to 2850fps. No matter what I did, go over that and groups stink.

The 223 will easily push a 75gr Amax to 2950fps and an 80gr Amax to around 2900fps. That is within SAAMI ranges. Some rifles of course can go faster.

New 223 bullets have BC that are higher/equal so with achievable ACCURATE velocity, it should have a ballistics edge.

A fast 223 trumps a slow 308. If they can both achieve ideal velocities, then for me the 223 still wins because of much lower recoil.

In Canada, we really don't get to experiment much beyond the 155gr bullets because of the rules. However, comparing wear and tear on the shooter, I much prefer the 80gr 223's. I think the 208gr 308's fatigue would negate any increase in potential wind bucking over the course of a match. OUCH.

For a long time the AR was laughed at in Service rifle type comps, now it dominates.

I think in the long run, lowering recoil is the best way to help improve your scores. You only need to flinch once to loose the match.

Jerry

John Kielly
01-10-2008, 05:34 PM
I was just wondering if the .22 calibres are so good in all conditions, why did anybody bother to invent the 30BR?

mysticplayer
01-10-2008, 06:07 PM
I was just wondering if the .22 calibres are so good in all conditions, why did anybody bother to invent the 30BR?

The 30BR is a solution to a particular 'game'. For its intended use, short range score shooting, it works wonderfully. Many consider it THE cartridge for that task.

However, for LR score, the ballistics are so poor that you would loose points due to shots being blown around. You still got to be able to put the bullets into the scoring ring.

For F class, the rules create a niche for the 223 and 308. From here, participants figure out what is the better mousetrap. That leads to innovations especially in bullet tech which changes what is the better mousetrap, which leads to more innovations etc.

If we somehow get a 'magical' powder that allows a 223 to push a 80gr VLD to 3100fps but doesn't improve the 308, there will be very few 308 shooters within a season.

F(F or TR) is alot like stock car racing. Everything is very closely regulated (at least in Canada) and quite 'low tech'. Racing is very close. There are many innovations to try and squeeze the 'nth degree out of everything. Gains are relatively small.

F(O) is like F1 racing. Very few boundaries. Where technology can run rampant. Performance is spectacular.

Like all games, there is always a 'best' combo to meet a set of rules. Change the rules/tasks, change the best combo.

Jerry

PS if for some bizarre reason the F class rule makers merged both classes into F(O), how many shooters would hang on to their 308/223 rifles?

John Kielly
01-10-2008, 06:48 PM
:confused:Jerry,

I was aware of that, but likewise I was aware (as a former TR tragic myself), that the .223 was relatively handicapped by the physics of the game compared to the .308, facts which Travelor seems reluctant to accept, as I did mention them on the LR forum.

Remember, we're discussing ultimately performance at 1000 yards.

Physically, the .223 case is approximately half the capacity & otherwise dimensionally similar to the .308, therefore is ultimately disadvanted almost twise as much as the ,308 with respect to intrinsic variables:

(1) The plus or minus error of his powder metring device (thrower, measure, whatever) will be identical whichever he loads, but will potentially cause about twice as much velocity variation as it will with a .308 case.

(2) Projectile eccentricity (out of balance) will be more critical in the smaller calibre

(3) Case tolerances can be expected to result in twice the percentage volume variation in the smaller case

(4) Case preparation variances are liable to result in greater neck tension variations in the smaller case than in the larger

I imagine that there might be other similar possibilities, but perhaps these will do for the moment. In any case, they demonstrate that the smaller case is substantially more difficult to load & equally more likely to generate '"stray" shots. I haven't dared even consider the effects of positional variations & other user generated differences.

Please remember also that we're not discussing preparing a handful of identical cases & reloading them for each detail here. TR & F/TR generally necessitate having maybe 200 rounds available for a state championship & preliminary matches.

Finally, while I note that the term anecdotal was mentioned somewhat disparagingly earlier, I point out that here in Australia, not one major championship (target rifle or F Open [equivalent to F/TR]) has ben won with the .223. Not one premier shooter uses the calibre.

I feel that there's more than anecdotal significance to that.

mikecr
01-10-2008, 07:03 PM
Why would you think the 30br represents anything good ballistically?
There is absolutely nothing a 30br could do over ANY other cartridge, except punch bigger holes. Thats it.

If the rules required shots to be completely inside the rings, some would head toward 17PPC or some BS like that. Just the nature of competition I guess. To get an edge no matter what.

roninflag
01-10-2008, 07:41 PM
i don't know what load you could get 2900 out of a .223 with an 80 grain bullet. interesting. in flagstaff the wind is quite challenging. so b.c. plus velocity helps a lot. the match in may has a possible 300 ponts . the 223's have never even got 150 points. the 300 win with 210 at 2900 the 6.5-284 with a 139 or 142 at 2900 or the 7mm 168 at 2900 really do a LOT BETTER. THE WINNING SCORE WITH THE 7MMrem ( 284) WAS TWICE THE NEAREST .223. . RONINFLAG

mysticplayer
01-10-2008, 08:16 PM
i don't know what load you could get 2900 out of a .223 with an 80 grain bullet. interesting. in flagstaff the wind is quite challenging. so b.c. plus velocity helps a lot. the match in may has a possible 300 ponts . the 223's have never even got 150 points. the 300 win with 210 at 2900 the 6.5-284 with a 139 or 142 at 2900 or the 7mm 168 at 2900 really do a LOT BETTER. THE WINNING SCORE WITH THE 7MMrem ( 284) WAS TWICE THE NEAREST .223. . RONINFLAG

We are not debating the difference between an F(TR) vs an F(O) cartridge. The F(O) is far easier to drive thus the cartridges are separated for scoring/trophies.

The question is whether a 308 due to its heavier bullet offers a ballistic advantage over the lighter 223. Does inertia change the effective BC of a bullet?

As for that 80gr load, some are going faster!

What I am describing is easily achieved using Varget or Re15 in a reasonble length match barrel. No difference then the 2900 to 3000 fps 155gr loads achieved in the 308W.

John K, case and ammo prep is up to the loader. All cartridges can be held to the same level of accuracy/tolerance so I don't buy a larger case/cal being superior.

If so, how do you explain the 6PPC. Seems to be accurate enough. Or the 6BR that IS used by a number of shooters in F class. No they don't load at the range anymore then you or I.

Use the right tools to achieve the desired results. A 223 can be made just as accurate as a 308.

Time will tell if the new VLD 22cal bullets will better the 308. More shooters, especially young shooters are trying this game through the lower recoiling 223. Will they eventually grow the 223 into a dominant cartridge?

The things that will never change is the 308 cuts a bigger hole and it will always recoil more. The ballistic issues will take a lot more shooting to figure out.

I do know a shooter who did research on this matter with Sierra. His conclusion was the 80gr MK dropped less then the 155gr MK at 1000yds using conventional load performance.

Go figure...

Jerry

milanuk
01-11-2008, 01:09 AM
Jerry,

Thanks for making that point. Every once in a while I think people forget the scope of the sandbox we're dealing with here in F/TR.

I have several .223s here... guess I better get busy working on some honest-to-goodness 'long range' loads for 'em ;) For the most part I've played pretty conservative w/ my 600yd loads in my Service Rifle - loads widely published on the 'Net shoot better than I can hold with it. With a scoped F/TR rifle that might change.

We're starting to hold regular 600yd monthly practices so I'll should get a good opportunity to compare against other calibers throughout the year.

Monte

mysticplayer
01-11-2008, 12:52 PM
Milanuk, good luck with your 223 ventures. I am still working on short range testing. Winter has set in so LR site is under snow. Love to hear about your 600yd testing.

I suggest you give the Amax 75 and 80gr a try. The poly tip does improve their ballistics. How much? That is the question. I feel that their BC rating is very conservative.

Testing other Amax bullets, the drop mimiced a G7 trace vs a G1. The BC value was correct though so the comparative G1 BC is substantially higher.

Looking at the shapes, the 75gr Amax is similar in profile/length to the many 80's and the 80gr Amax similar to the 90's. I feel that the 90's are getting too heavy for this case but they are certainly working for some.

My goal is to get these bullet out to 1000yds and see what the drops work out to. My SWAG puts the 80gr Amax BC closer to 0.5 which being lighter also means going faster. The Best of both worlds.

Will do a comparo with 80gr Bergers and hopefully 90gr Bergers if I can get my hands on them.

For such a small case, I have always found the 223 to be very primer sensitive. I use CCI BR4 in the warmer temps and 450's in the winter. Has shown much better ignition when things get cold. might try and get some Fed's too.

Powders are a toss up using the 75gr Amax with Benchmark and Varget. If you have a gas gun, go Benchmark - Varget/H4895 too bulky. You can seat a 75gr Amax to AR mag length and still not have issues with powder compression. You might be able to reach bolt gun velocities too with a pressure valve on the gas block.

I think Varget is the choice for 80gr and heavier slugs. Will also try Re15 as that is reported to give higher velocities in some guns.

IF real world BC of the 80gr Amax hit 0.5 AND a muzzle velocity of 2900 or faster, this will be a formidable combo in F(F)...at least on paper.

The question will be how much those little pills get bounced around in the real world vs the 308.

I am betting the math is not wrong.

Jerry

http://www.6mmbr.com/223Rem.html

bsl135
01-11-2008, 08:06 PM
I've got a few thoughts on comparing these two cartridges.

First, a few clarifying points: I'm comparing the .223 cartridge to the .308 Winchester cartridge. In other words, NOT .22 caliber vs .30 caliber. So we're not talking about .22-250's, or 300 Win Mags, etc.
Also, some people have only been considering the .308 with the 155 grain bullet, and the .223 with 80 and 90 grain bullets. As was pointed out, this is not really a fair comparison because the 155 grain bullet is quite light for the .308. As far as I'm aware, there's no restriction on bullet weight in F-class shooting of any kind (I stand to be corrected here). The 155 grain limit on .308 bullets is only for international Palma shooting which isn't being considered at present.

So, I'll begin the comparison by looking at the bullet weights, and what's meant by 'heavy for caliber'. We know that the 155 grain .30 caliber bullet is 'light for the caliber', and the 90 grian .223 bullet is 'heavy for the caliber'. Below are some comparisons that illustrate 'equivalent' weights for caliber. For example, if you scale that 155 grain .308 bullet down to .224 caliber, it weighs 60 grains. Here are some more 'equivalents':

-----Equivalent bullets (mass)--
.308 caliber---------.224 caliber
---155----------------60
---175----------------67
---185----------------71
---190----------------73
---200----------------77
---210----------------81
---220----------------85
---240----------------92
-------------------------------

The above table just illustrates what bullets are light and heavy for the caliber. Another way to think of bullet 'equivalence' is in terms of BC. In other words:
"How heavy does a .22 caliber bullet have to be to have the same BC as a 155 grain .30 caliber bullet?"
The answer to this question depends on the form factor (shape) of the bullet. For bullets having similar shapes, the comparison illustrated by the next table:

-----Equivalent bullets (BC)---
.308 caliber---------.224 caliber
---155----------------82
---175----------------93
---185----------------98
---190----------------101
---200----------------106
---210----------------111
---220----------------116
---240----------------127
-------------------------------

Again, this table only holds when you're comparing bullets of the same design (VLD's, Matchkings, Amax, etc).

So according to the above table, a .30 cal 155 grain SMK has the same BC as an 82 gr .224 SMK. According to Sierra's website, the 155 has an average BC of .437 over the full range velocity and the 80 grain bullet has a BC of .404 over the full range velocity.
There are several reasons why the BC's aren't exactly as predicted in the table:
1. Slightly different form factors (shapes)
2. 80 grains vs 82 grains
3. Uncertainty in the advertised BC.

Even though the numbers aren't exactly as expected from strict scaling, they are within 8% of expected.

Getting down to the question of what's better (.308 or .223), I see two ways to look at it. We know we're looking at a heavy .223 bullet. Question is, are we better off with a light, fast .308 bullet (155 at 3000 fps) or a heavy, slow .308 bullet (190 at 2700 fps)?

Before we get too heavy into the analysis, we have to know what measure of performance is most important? I mean, when we say "which is 'better'"? What do you mean? Less drop? Less wind drift? Higher kinetic energy?

I think as target shooters competing at known distance, we can agree that drop is a non-issue.

It doesn't take much kinetic energy to make it thru the paper, so that's a non-issue.

As long as there's at least 1120 fps of velocity remaining (speed of sound), then velocity is a non-issue.

For certain, the most important measure of merit for bullets used in long range competition is WIND DRIFT.
*This assumes that both rounds are capable of the same level of inherent accuracy, I'll address this later. Right now, we're just considering basic ballistic performance.

I'll proceed with the analysis using wind drift as the sole measure of merit.

What kind of wind drift does the .223 have?
From what I gather, the .223 is capable of achieving 2900 fps with 80 grain bullets. Let's consider SMK's for this example. Using MV = 2900 fps, and BC = 0.404, the 80 grain .224 caliber bullet drifts 118 inches in a 10 mph crosswind at 1000 yards (standard atmospheric conditions). So that's what we're trying to beat with the .308.

Let's try the fast, light bullet first.
Using 3000 fps muzzle velocity, and BC = .437, the 155 grain bullet drifts 100 inches in the 10 mph crosswind at 1000 yards. This is 17" less (15% less) than the .223.

Now let's try the slow, heavy bullet.
Using 2700 fps muzzle velocity, and BC = .524, the 190 grain bullet drifts 91". This is 26", or 22% less than the .223 with 80 grain bullets.

So in either case, the .308 is superior to the .223 in terms of wind drift.

One counter point to this analysis is: The advertised BC's aren't accurate.
Granted. But they aren't off by enough to negate the results.

Now, there are other important things to consider other than wind drift. Effects of recoil for one. It's been stated that the higher recoil of a .308 can cause a shooter to not shoot as well as he could with less recoil. This is a very good point. Every shooter has to HONESTLY asses their own ability to manage recoil and make their cartridge selection accordingly. If the heavier recoiling rifle causes you to execute shots poorly, then better ballistics are irrelevant! But it doesn't change the fact that the ballistics of the heavier round are superior.

Another consideration is the inherent accuracy of the rounds. I've heard arguments for both sides. The popular contention is that the smaller caliber is inherently more accurate than the larger .308. No reason is given, it just seems to be an accepted fact. John K. has a very well reasoned case for the larger .308 being more inherently accurate (due to given errors having less of an effect, percentage wise on the larger round, etc). Although this is a reasonable statement, my experience has shown the smaller calibers to be more accurate in all classes of guns. Go to the gun store and buy two lightweight hunting rifles, one chambered in .223 and one in .308. 9/10 times, the .223 will shoot better groups than the .308. Now have a world class gunsmith build two identical target rifles with all the best components. One in .223, one in .308. My money's still on the .223 shooting tighter groups with the same level of load development, etc. I think the 'percentage' effect that John describes is valid, but is overpowered by other effects that favor the smaller caliber. Recoil is one thing that effects not only the shooter, but the rifle's ability to remain rigid while delivering the bullet. If forced to give a reason why I believe the smaller round is inherently more accurate, I would point to recoil.

The following statments sum up my analysis of the .308 vs .223 debate:

1. Wind drift is the most important measure of ballistic merit for known distance target shooting, and the .308 is superior to the .223 in this respect.

2. The .308 is better (in terms of wind drift) with heavier bullets going slower than light bullets going faster.

3. The .223 has less recoil than the .308, and this can be a more important factor than ballistic performance. This depends on the shooter.

4. The smaller round seems to have more inherent precision than the larger round. I don't consider this to be very important compared to wind drift though. Reason being: The precision difference isn't very big, and most points will be lost to wind anyway.

Conclusion:
If you can manage the recoil of the .308, it's the better option for long range target shooting.

Keep in mind that the final decision comes down to a personal choice. There's no right or wrong answer to the overall question: which is best? (like Ford vs Chevy) We know which is best for wind drift, and we know which is best for recoil, but these are just factors to consider. A GOOD decision is always a careful compromise of all the factors involved. If you can shoot better with the smaller round, then that's the best choice for you even if the majority of the winners are shooting something else.

Take care,
-Bryan

PS
All of the ballistics numbers were run on the JBM online ballistics calculator (http://www.eskimo.com/~jbm/ballistics/traj_basic/traj_basic.html).

mysticplayer
01-11-2008, 10:32 PM
That was a very indepth study of both options. Well done.

Now let me throw in a few wrenches to muddy things up again.

1) 80gr MK is the lowest BC bullet in this class. The 80gr Amax is .45 to .49 (depends alot on the pipe). The 80gr Berger is listed at .47ish.

These two bullets put the BC of the smaller cal right in there with the 180/190gr match bullets.

2) you have chosen a 223 velocity that is SAAMI speced. However, the 308 velocity is HOT. SAAMI puts the 308/155 combo in the 2800/2900fps range. Let's say 2850fps.

For the 308/190, SAAMI/load manuals peg this at 2400/2500fps. Say 2450fps

Don't get me wrong, I know all about what the 308 can do (been there and got the loose primer pockets to show too) but that argument can be applied to the 223 as well ie 80gr at 3000/3100fps.

Redo the numbers using a 80gr Amax or Berger at 2900fps (readily achieved in a 26" barrel), the 308/155 at 2850fps and 190 at 2450fps.

How about 90gr Berger (.517) at 2900fps, 155gr at 3000fps, 190gr at 2650fps?

AHHHHH, things aren't so clear cut anymore are they?

And that's my whole point. It is not an absolute that the 308 IS better. So much matters on the bullet, load, and accurate velocity. Some barrels are fast, others slow.

What will the velocity be when the rifle is shooting its best?

What will happen to the 308 barrel as it heats up much more over a 22rds relay? Will it walk all over the target?

How well will the shooter fair 45 rds later?

As said before, a fast 223 will trump a slow 308.

The only definites are the 308 makes a bigger hole, heats up barrels, and recoils more....

F(F) or F(TR) is one of the most interesting precision shooting comps because you have two very different cartridges that are so equally matched. Fine tuning and oddities can push one infront of the other then back again.

Unfortunately, where I compete, all F class shooters are lumped together so I shoot F(O). Like to see what the scores are like when there are good numbers of each cartridge competing on the same weekend.

Jerry

bsl135
01-11-2008, 11:36 PM
I hate wrenches!!!



1) 80gr MK is the lowest BC bullet in this class. The 80gr Amax is .45 to .49 (depends alot on the pipe). The 80gr Berger is listed at .47ish.

These two bullets put the BC of the smaller cal right in there with the 180/190gr match bullets.

C'mon Jerry, you know what I'm going to say to this...
Of course if you compare .223 VLD's to .308 non-VLD's, the .223 looks good. If you compare apples-to-apples (VLD's to VLD's), the 190 grain .30 caliber bullets still has a higher BC than the .224 (.574 for the 190 VLD compared to .47'ish for the 80 grain VLD)



2) you have chosen a 223 velocity that is SAAMI speced. However, the 308 velocity is HOT.

Granted. I don't have any experience loading the .223, so I didn't know where 2900 fps is in the spectrum of realistic pressures, it just sounds hot to me. In fact, my Sierra reloading manual gives a max velocity of 2600 fps for the 80 gr SMK. Granted, the test bble was a 20" Colt. The Nosler manual doesn't list an 80 grain bullet, heaviest is 68 grains, max velocity 3030 fps from a 24" test bbl. Assuming equal pressure and KE at muzzle, this corresponds to just under 2800 fps for an 80 grain bullet. All this leads me to believe that 2900 fps is quite hot for the little .223, but I've never done it.

The .308 velocity is on the warm side, but you know it's not too hot. Lots of guys get more than 2450 with the 190's too.


And that's my whole point. It is not an absolute that the 308 IS better. So much matters on the bullet, load, and accurate velocity. Some barrels are fast, others slow.

What will the velocity be when the rifle is shooting its best?

I see what you're getting at here. It's possible that a .308 shooter has the misfortune of getting a bbl that likes slow loads. It's also possible that a .223 shooter will luck out and find a bbl that hums at max pressure. So it is possible for the .223 to beat the .308 in the wind, on an odd occasion. However, the odds are in favor of the .308. Both my Palma rifles and most others that I've known have liked 2950 to 3000 fps just fine with the 155's. I don't have much experience with the heavier bullets. The limited experience I do have indicates that 168's and 175 Bergers did best at high pressure.

What I'm saying is that if it were very common for .308's to be more accurate at lower velocities, then your point would be stronger. Like I said, I don't have any experience with the .223, so I don't know what pressures they like. If you compare max charges for both, or the same % of max charge for both, and the same class of bullet (SMK, VLD, etc) I think the .308 will always have less wind deflection to some degree.


What will happen to the 308 barrel as it heats up much more over a 22rds relay? Will it walk all over the target?

This is a good point I didn't think about. The pace of shooting can be quite a bit faster in F-class than slow fire prone. I can see barrel heating playing a role more for the larger bore.


How well will the shooter fair 45 rds later?

Important consideration, it depends on the shooter. I know (few) guys who shoot 220 and 240 grain bullets out of big magnums all day long and turn in tremendous scores. I also know some who have tried and couldn't handle it.


As said before, a fast 223 will trump a slow 308.

I agree this is possible. But can you be sure your .223 will be 'fast'? More importantly, do you want to gamble on everyone else's .308 being slow?


F(F) or F(TR) is one of the most interesting precision shooting comps because you have two very different cartridges that are so equally matched. Fine tuning and oddities can push one infront of the other then back again.

Again, I agree. There are many things in favor of the .223 and a lot of shooters would do better with it.

However, I maintain that in the long run... on average... the .308 is better in the wind... even if that's the only advantage of the larger round.


Unfortunately, where I compete, all F class shooters are lumped together so I shoot F(O). Like to see what the scores are like when there are good numbers of each cartridge competing on the same weekend.

That's too bad. I'm sure those who shoot .223's and .308's know who each other are, and compare notes afterwards, even if it's not an official class.

Thanks for adding your thoughts Jerry. I know you are a very good shooter, and you know what you're talking about. In the hands of a really good wind reader like yourself, I wouldn't bet against the .223! I just wish I knew more about the pressures and velocities that the .223 is realistically capable of so I could better understand the comparison.

-Bryan

milanuk
01-11-2008, 11:43 PM
Brian,

One thing to consider - 155gr is the limit for F/TR north of the border. As I understand it, 175s or 190s would put one in the Open class. Same for bullet weights above 81gr in .224 cal.

I think this might be getting into the area of calculated vs. empirical data. As an example: you can calculate how the .223 *should* be better til the cows come home. A fair number of people (NRA High Power) seem to have tried that route already, and opted for something else . A few people maintain that they shoot better/ use less wind/ have better looking kids using the .223... but the majority seem to have moved back to .308. Similarly, I've spoken with some prominent Palma shooters who provided anecdotal tales of shooting 155gr loads on the line side by side with shooters using 190gr loads. They came off the line with less than a 1/2 minute difference in windage, but a steady diet of 190s proved harder on the barrel over time. Such tales from shooters of that level of experience are hard for me to completely discount.

There had been some smack-talking going on before SOA/FCNC in '07, the usual tripe from the heavy bullet crowd about the whoopin' they were going to lay down on 155 shooters ;) There was discussion about getting some people from each camp together during the squadded practice day before SOA and after getting both shooters centered up for teh conditions, have them hold center and fire on command from a coach. Subsequent plotting of the shots fired at the same time under the same condition would hopefully provide some 'hard' data vs. calculated or anecdotal. Sadly, no heavy bullet shooters showed that day, and the test never happened. FWIW... there was *one* .223 Rem @ FCNC, and suffice it to say that while Lapua 77s did indeed raise some eyebrows @ 600, 1000yds was a whole 'nother story. I do wonder how he would have done w/ a more suitable bullet.

It would be an interesting (and hopefully educational) project for someone to put together locally... even if just at 600yds. Chronograph the loads before hand to get an average MV, have shooters firing known good loads from known good rifles, and line up a .223 Rem shooter firing 80s, and a couple .308 shooters firing 155s vs. 190s or 210s. I'd be willing to try it but I can only fire one gun at a time ;)

In the end... I think it comes back to what F/TR is all about (to me)... you can worry about theoretical 'advantages', or you can hold harder and read the wind better, and still end up coming out smellin' purty good ;)


Monte

mysticplayer
01-12-2008, 02:22 AM
milanuk, that is such a simple solution to a very complex problem. The key is to ensure that all test rifles can shoot similar accuracy levels, say 1/2 min so you don't get huge distortions due to mechanical accuracy problems.

zero all the rifles for elevation at distance but retain a zero windage setting. Line them up, call and fire. See where the bullets land. Repeat 10 times on maybe two targets so you can get some idea of how things fared. Note wind conditions for each shot to help diagnose relative wind drift.

I'll see if I can get some 308 shooters to help with a test in the spring.

Bryan, thanks for your vote of confidence on my wind reading skills. You give me more credit then I deserve. It is surprising how well you can do when you just close your eyes and pull the trigger.:D

As for not knowing what type of 223 I would have, the answer is preparation and is no different then any shooter on the line.

If I were to campaign a 223, I would have the best damn 223 I could make on the line. I would know that I had a rig that was competitive or else why even bother shooting it?

Up here, we are limited to 80gr 22cals and 155gr 308's for F(F). That narrows down things alot. Now you just have to optimise your poison and learn how to drive it.

As for 308's performing better then SAAMI speeds, yep, that's a no brainer. However, I have been blessed with a few slow pipes so dud barrels are certainly out there.

Recoil and barrel heat are going to be the limiting factors in the super heavies in a 308. The case capacity is simply too small to get these bullets moving fast WITHOUT excessive pressure.

No matter how fast you go, if that barrel starts warping after 12rds on a hot summers day, you are pooched. The 223 has a huge advantage here.

What I think SHOULD happen is that both the 223 and 308 be regulated for muzzle velocity to keep all shooters safe.

Yes, we can run up the velocities with 100% function but how much pressures do these loads actually have?

I know that proof loads will extract easily from a commercial action let alone a BR quality action. No primer pocket leaks. No real obvious pressure signs.

A 155gr at 3000fps or faster in some rifles might just be proof load type pressures. There is simply no way to know by guessing.

I have heard of some shooters saying their 208gr loads at 2700fps were without pressures signs. I don't care if you use a 32" barrel, that is in 300WM territory.

Here is something that should be of interest to those looking for 'screamer' performance.

The 223 with its smaller case head and small primer actually can withstand MORE pressure. The brass around the case head is proportionately stronger. The bolt thrust is less and the camming force of the bolt higher on the case head.

Get creative with throating lengths and you can squeeze another grain or two into that case. In such a small case, that is ALOT of juice.

Why some are pushing 80gr bullets to 3000/3100 fps.

SAAMI, nope. Safe, debateable.

I am sure someone will come up with an over the top receipe that might even shoot accurately.

That person may even win a few matches and then...

We have PPC type time bombs in F class rifles.

I am going to do some testing this summer with my 223 and see how it does.

No matter which way you go, 223/308, neither is a wind bucker and you got to drive well to score.

My 6.5 and 7 Mystic shoot with 1/2 the windage of my 223 and 308. That makes life a whole bunch easier and so much nicer to drive.

Jerry
http://www.6mmbr.com/223Rem.html

Lots of 223 info here.

Travelor
01-12-2008, 08:17 AM
Guys, I shoot both guns and actually prefer the 308 as I have a lot more experience with it. This journey started when I bought my wife a Savage Model 12 LRPV in 223 with a 1:7 twist barrel (she did not like the recoil of the 308) and immediately the fellow shooters started telling me how it would not work at 1000 yards due to wind drift even though the QL and QuickTarget tables indicated it would be on par with my 308 and 155 gr. SMK's at 2950.

The point of my original question was to get information as to why the ballistic tables and reported range results varied so much. The discourse in the thread and the one over on Long Range Shooting has been very informative and I really look forward to seeing the range results mysticplayer will report on.

Thanks for all the discussion. I am learning a lot!

George

PEI Rob
01-12-2008, 11:42 AM
Gentlemen, the 155gr Lapua has a BC of .508 and shoots great at 2950+, lots of DCRA guys here do just that easily.

I'm fairly certain one can get 2900 out of a 223 with heavies, kind of ties it up doesn't it.

Its all good,
Cheers,
Rob

mysticplayer
01-12-2008, 03:56 PM
Travelor, since you have both cals, why not do the test next time you are at the range. Add in a few more shooters to increase the tests results. Even with the same bullet and similar velocities, I bet you find that the drift values vary between rifles.

Chronie a few shells from each shooter at the time of the test using the same chronie.

All go with zero windage adjustment on a windy day. Aim dead center, shoot at the same time and have the shot scored. In 10rds, it will be clear which is drifting less. Change shooters on each rifle and repeat so there is no bias on the equipment.

That would be alot faster then waiting for me as I would have to get together in the spring and I would be limited to just two rifles.

Ballistics programs are notoriously simplified. ALOT of variables get avoided or else we would need super computers to crunch. I have used most ballistics program and they all produce similar results. In many cases, that print out has little to do with real world shooting. I adjust my drop tables for my particular set up.

We know that the value of ballistic coeffecient is 'dimensionless' so bullet mass should not matter. Only the planform and its relative drag determines how it flies through the air. I am sure any rocket scientist will tell you that is overly simplified. The G functions we use are also simplified/inappropriate and may not account for new bullet shapes - big reason ballistics programs are not exact in the real world.

With the 223 and 308, both are ballistically very very close - at least on paper. However, I am unaware of anyone taking the time and doing a proper test to compare relative wind drifts. We do this everytime we shoot and compare notes but the amount of error is enormous.

So the easiest solution is to test side by side under the very simple process described above. Holes in paper are going to resolve alot of math.

Jerry

LarryBartholome
01-12-2008, 06:42 PM
Jerry,
“Holes in paper are going to resolve alot of math.”

Holes in paper can tell the tale, but it may just be fiction if the test is not done correctly. I feel it is not enough to rely on a shooters zero to help determine wind drift. To get an accurate idea of the wind drift of the two calibers would require chronographing the rifles the morning of the test to confirm the speeds are really where you want them. Then zero the rifles (preferably in a no wind condition) at say 300 yards and synchronize them by volley firing; then moving back to 1,000. Re-volley fire (if possible in no wind) to check no wind zeros (they can change between ranges) and then volley fire a good number of shots to complete the test.

A group of friends and I did this a little over a year ago to test 6.5, 7mm and 30 cal drift. It was written up in PS magazine. Quite an interesting day! I must say the weather worked out perfectly for us going from zero all morning and part of the afternoon and then abruptly to 4 moa and then up to 10 moa. I don’t ever expect to have that happen again.

It would be interesting to see the results of a .223 vs. .308 test done accurately.

Larry Bartholome

mysticplayer
01-12-2008, 07:57 PM
Any chance of posting some of your results. NO PS mag around here.
Thanks,

Jerry

bsl135
01-13-2008, 01:26 AM
Monte,
First of all, thanks for informing me about the 155 and 80 grain limits you have in Canada. I wasn't aware of this restriction, and it's important to the potential comparison of the .308 and .223.

Jerry and others,
Your lack of confidence in ballistics programs is understandable. Many people use these tools, but there are a lot of pitfalls that keep the average guy from realizing the full potential. Here are a few examples of common errors:
1. Atmosphere. The atmosphere will default to standard sea level conditions unless you input something else. The standard atmosphere at sea level is far denser than what we usually shoot in (hot summer air, possibly humid, and some amount above sea level). If you don't input the correct atmospheric conditions, the results of the ballistics program will not be accurate.

2. Muzzle velocity. To avoid a long discourse on chronograph accuracy, I'll simply say that it's possible to have significant error in velocity measurements. Even if the chronograph is accurate, how many shooters take the time to account for the velocity lost between the muzzle and the chrono? This is roughly about 10 fps over 5 yards. Obviously, you can't expect the program to be accurate if the MV input is incorrect.

3. Zero range. How carefully do we insure that the value input for zero range is accurate?

4. Scope tracking. Adjusting 30+ MOA from a 100 yard zero to 1000 yards is asking a lot of a scope. The higher end scopes can be expected to be better at this than less expensive ones, but who takes the time to confirm the scopes MOA adjustments over the ENTIRE range of travel? This becomes an issue when you compare MOA 'come-up' on the scope to drop predicted by a ballistics program. The only way to eliminate the scope adjustment variable is to zero a known distance high at close range to impact at range, or zero at close range and hold over at a known distance at range. This removes the scope adjustments from the problem.

5. Winds. For now I just mean vertical winds that could deflect the bullet up or down, effecting the drop and causing it not to match the ballistics program predictions.

6. BC. There are several problems here. The most common 'violation' is using inaccurate BC. It's not the users fault, we're at the mercy of the manufacturers who are obviously compelled to advertise high. Another problem is that G1 BC varies greatly with velocity. Sierra addresses this problem by quoting different BC's for different speed ranges. Many shooters don't understand how to use this information, and just use the high velocity BC for all calculations. The proper way to do it is to either enter the multiple BC's, or average the BC's over the expected velocity range. A common example of this is using .450 for the BC of the 155 SMK. .450 is only the BC at high speed. Over 1000 yards, the average BC is more like .437. That error (.450 vs .437) is not the ballistic program's fault, it's erroneous input.

7. BC. Another problem with BC is that we're using the wrong standard (G1) for long range bullets. The G1 standard is for short nosed, flat based bullets and very poorly fits the drag model of our long range bullets. This poor fit is the reason why BC has to be defined in terms of velocity. If we were to use a more fitting standard like the G7, the programs become much more accurate. It's too bad the industry is so stuck on G1. Here the shooter has no option to improve the accuracy of the program. Most programs can use BC's referenced to the G7 standard, but how do you know what the G7 BC is? Not easy.

8. Rifle support. I've never done this test, but I think if you zero a rifle at 100 yards from a benchrest, then lay down in the prone position with a sling/coat, etc and shoot at the same 100 yard point of aim, the rounds will not impact the same point as those fired from the bench. This is also not the fault of the ballistics program.

So there are many reasons for the print out of the ballistics program not to match real world observations. That doesn't necessarily mean the ballistics program is lacking. It's just like any other tool: you have to use it properly to get the desired results.

So we turn to the 'real world'. There's a lot of talk about shooting things side by side, etc. I agree with Larry (great article by the way) that it's a very involved process to do this test properly and effectively. There are many steps required to 'calibrate' the rifles and zero's, etc before the test. I agree that GOOD empirical data is the best kind, but it's not easy to get. Just like with computer programs, there are a lot of 'gottchas' that can make the test invalid without you even knowing it. Many people who are thirsting for the empirical data will take the results as gospel without questioning the credibility of the test.

In order to determine the wind drift of one bullet over another, here's what I WOULD DO...
MEASURE the G7 BC of the bullets to be compared. This is a more practical test than testing for wind drift. Less spread in the data, shorter ranges required, etc. Once the BC's (referenced to the proper standard) are known, then use a ballistics program with accurate inputs to calculate the wind drift of the two rounds. Many people refuse to believe it, but the often misunderstood BC is a very important piece of information.

For example, BC is not unit-less. It has units of mass / area. It does include a dimensionless 'form factor'. This form factor is what relates the drag of the bullet to the 'standard' (G1, G7, etc). The form factor is constant if the bullet is similar to the standard. If the bullet is different from the standard (as in the case of long range bullets and G1) the form factor varies, and this is what causes BC to vary.

There's really far less mystery involved in ballistics programs than most people think. All a ballistics program needs to know in order to calculate: downrange trajectory, velocity, time of flight, and flight path angle is: BC (which includes information about the caliber, mass, and aerodynamic drag of the bullet), atmospheric properties required to calculate air density, muzzle velocity, and a description of the geometry (sight height, max range, zero range, etc). With those input parameters, the equations of motion can be solved in any number of ways (closed form, numerical integration, etc) for the outputs of interest. Bullet mass/inertia IS accounted for in the BC. There are no physical mechanisms that 'fall thru the cracks' of modern ballistics programs.

Having said all that, the wind still gives us problems due to it's fluid nature. What I mean is, when you describe wind to a ballistics program, you give it a speed and direction, and the program applies the same values for the entire trajectory. We all know this is a poor model of reality. Also, vertical winds are present in the real world, and are not addressed with typical ballistics programs. IF there were a situation where wind was steady in speed and direction, and consistent with height above ground, the ballistic program would give accurate answers for wind deflection.

I've sent a series of 3 articles into PS magazine that describe my BC test results for 3 Palma bullets: Berger, Sierra and Lapua 155's. My testing methods are very precise (I can repeat BC measurements within 1%) using a system of acoustic time of flight sensors spaced in 200 yard increments from muzzle to 600/1000 yards. These articles should be appearing in PS within the next few months. Measured G7 BC's and average G1 BC's are provided along with effects of meplat trimming and pointing on BC. Wind drift and drop comparisons are made. Also, comparisons are made between trajectories calculated by G1 and G7 BC's. The articles are very relevant to this discussion.

Take care,
-Bryan

Travelor
01-13-2008, 08:04 AM
Jerry and others, I will test at the range.

Our range is currently 300 yards and is in the process of being increased to 600 yards. Construction is well underway and should be done in 2 months or so depending on weather and contractors. By then my 223 will be back from Larry Racine and I will test my 308 and 223 in a heads up test at 600 yards as soon as possible and report.

We have access to a 1000 yard range, but it is a National Guard range and we can't get on it except for Matches so it will not be possible to do this test before our next Match their in March and at that time there are no benches to shoot from (I know, some would rather shoot prone).

I like the idea of getting now wind zero's and then shooting in wind side by side with no wind correction in the rifles - this should tell the tale at least in my guns.

This thread is getting better each day!

George

manitou210
03-30-2008, 06:30 AM
This load might give the .308 a little competition;

http://gunloads.com/modules.php?name=Gunloads&cmd=Gunloads&did=415

AlanF
03-30-2008, 08:44 PM
This load might give the .308 a little competition;

http://gunloads.com/modules.php?name=Gunloads&cmd=Gunloads&did=415

AR2208 is identical with Varget, so that load is slightly above the Hodgdon recommended max charge of 25.0gn for 80gn SMK. I think any comparison would need to use this as limiting factor?

Alan