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b moulds
02-26-2008, 06:42 AM
hello,
can anyone give advice on the b.c.s of the following bullets from actual firing tests &/or experience?
180 berger
175 sierra
168 berger
162 amax
possibly someone has calculated their b.c.s using the same method.
i have some old plastic point amaxes that are longer than a 180 berger. these might hold the wind better than heavier bullets out of a 284 win case due to a speed advantage.
are amax bullets as accurate as hollow points? they should have more consistent b.c. due to meplat uniformity. also, are these plastic pointed bullets reliable?
is the amax stable in a 1/9" twist?
any help greatfully recieved,
bruce moulds

JeffVN
02-26-2008, 10:58 PM
I am currently shooting the 7mm 180 Bergers in my 7WSM, and shot the 175 sierras before that. The sierra's shot right at 1/2 minute more elevation then the Bergers at virtually the identical velocities - 2,920-2,930 fps in Las Vegas, elevation 2,200 ft.

I use exbal as my balistic calculator and it hits the elevations for the Bergers pretty much dead on for elevation when i set the velocity 25-30 fps slower then I'm actually shooting. Hope that helped and iddn't just cause confusion.

JeffVN

J. Valentine
02-27-2008, 03:35 AM
hello,
can anyone give advice on the b.c.s of the following bullets from actual firing tests &/or experience?
180 berger
175 sierra
168 berger
162 amax
possibly someone has calculated their b.c.s using the same method.
i have some old plastic point amaxes that are longer than a 180 berger. these might hold the wind better than heavier bullets out of a 284 win case due to a speed advantage.
are amax bullets as accurate as hollow points? they should have more consistent b.c. due to meplat uniformity. also, are these plastic pointed bullets reliable?
is the amax stable in a 1/9" twist?


any help greatfully recieved,
bruce moulds

The 168 grain Berger VLD BC = .648
" 180 " Berger VLD BC = .698


Sierra .284 dia. (7mm) 175 gr. HPBT MatchKing
Ballistic Coefficients to Velocity Bounds.
1. 0.608 at 2100 fps. and above.
2. 0.582 from 1530 to 2100 fps.
3. 0.532 from 1300 to 1530 fps.
4. 0.500 at 1300 fps. and below.

Hornady 162 amax BC = .625
These are the advertised BC's !

Tony Z
02-27-2008, 06:53 PM
I think Bruce was after real world BC. .648 for the 168 Berger is not in this world. .548 may be closer.

Tony Z.

J. Valentine
02-27-2008, 07:09 PM
I agree that you cant believe some BC numbers but I did state that they are " ADVERTISED BC values "
Anyway , why did you not post the information requested?

bsl135
02-27-2008, 07:17 PM
Bruce,
I have measured the BC's of all those 7mm bullets. Here are the 'as measured' G1BC values:
Berger 180: 0.659
Berger 168: 0.617
Sierra 175: 0.639
Hornady 162: 0.580

These values are all averaged between 1500 fps and 3000 fps.

The G1 BC's are the most familiar to us, but for projectiles like these, the G7 standard is far more appropriate. The benefit of using the 'appropriate' standard is that the BC's don't vary with speed, which simplifies comparisons. Here are the G7 BC's, also from 1500 fps to 3000 fps:
Berger 180: 0.337
Berger 168: 0.316
Sierra 175: 0.327
Hornady 162: 0.297

These values were measured over a minimum of 600 yards (some tests were at 1000 yards) at 200 yard intervals. Sample size is at least 6 each. I won't go into detail about my testing procedure except to say that it is repeatable within +/- 2%, so these values are the real world, measured BC's.

Of course, the results are specific to the lot of bullets I measured. The biggest variable among bullet lots (that affects BC) is meplat diameter. Below are the meplat diameters for the specimens tested:
Berger 180: 0.059"
Berger 168: 0.064"
Sierra 175: 0.063"
Hornady 162: n/a

If your bullets have different meplat diameters than the one's I tested, the BC's will obviously be different.

Personally, I shoot the Berger 180 VLD at moderate velocities (~2800 fps) from a .284 and find it to be great in the wind.

At long range, the added velocity of a lighter bullet (168 or 162) does not make up for the lower BC in terms of wind drift.

Take care,
-Bryan

a.JR
02-27-2008, 07:57 PM
We completed tests recently with the 2 Sierra's at 1000yds.. No body has yet to mention the speed at which the bullet shoots .. In these tests ( group only) we took a well known 1K light gun (shot down to just under 3.5in) ,developed the best loads it could produce over a 6 month period at both 500met and 1000yds ..Results are smallest group belongs to the 175SmkSmall margin) and the smallest averages belong to the old 168Smks(by a long way) .. These tests were all conducted with fully qualified and meplat uniformed bullets .The last test we did involved firing the 2 best loads at 1000yds with good test weather , back to back.. Results were 168 group averages of 4.200 ins (3.00ins of VD and 4.2 of windage, basically round groups ) ,for the 175 it was 6.5ins group (6.5 of vd and 4.0 ins of wind , mostly stacked). This is tipical of the 175 ,it would go from champion to chump at will, it's just that the champ status was about 1 in 8 groups ,.Most interesting part is the 168s arrived about 9ins further up the paper than the pointy bullet , so much for all those BC calculations ..My call on this is that the batchs of pointy bullets in 7mm that we have been able to buy here are unpredictable in their group performance compared to the old school bullets and i would much prefere to learn how to to shoot with a bullet that is consistantly predictable than one that cuts through the air like a Scramjet(and i learn every time i shoot )..JR..Jeff Rogers

bsl135
02-27-2008, 08:34 PM
Most interesting part is the 168s arrived about 9ins further up the paper than the pointy bullet , so much for all those BC calculations ..

Actually, this lines up perfectly with what I would expect based on the BC's.

Bruce didn't ask for the BC of 168 SMK, but I measured it at 0.567 which is significantly higher than what Sierra advertises. Now it's hard to model your test exactly because you didn't provide velocity data. However, the following is a likely scenario...

You're probably getting about 2850 fps from the 175's with 50.5 gr H4350. According to my calculations (using my measured BC values): in order to impact 9.0" above the 175's, the 168's would require a muzzle velocity of 2975 fps. This is likely near the velocity you were getting with 51.5 gr of H4350. In other words, according to the BC's I measured, and the difference in vertical impact that you observed, the 168's were likely going about 125 fps faster than the 175's, which is very believable.

Too bad you don't have any velocity data for those tests. Given MV, we could make a truly meaningful comparison.

By the way, the 168's at 2975 fps have 71.5" of wind drift (10 mph wind @ 1k yds) and the 175's have 71.9", so they're practically equal in terms of wind drift.

When I stated in my previous post that the heavier bullets always beats the lighter bullets in the wind, the 'assumption' was that equal powder charges were used. I'm still surprised that the 168's are so close to the 175's, even with 1.0 grain more powder.

I have to commend you on a successful test. Anytime you're 'chump' groups average 6.5", you're not doing too bad! Sounds like you got your equipment developed very well. How many shots were these groups?

-Bryan

a.JR
02-27-2008, 09:19 PM
Bryan ,This is not my gun , i was the one callin the shots ,so to speak on the load development .. The gun is an AUST LRBR Light Gun and is the same as all but one of the US sanctions(5 Shot)_.. the speeds to me are as unimportant as the BC figures ,we try with every cartridge to get to shoot to it's best at the highest speeds that the cases can easily withstand .. My real interest is in the speed (Load) is the one that makes the smallest consistant groups and nothing else ..My time spent shooting prone matchs are too tiny to call real experience ,so mabye you can win matchs with 6.5in + gun ,but in Benchrest your going to have to sharpen the pencil on most days to come up a winner .. I have owned the high speed ,high BC gun many times and found it to be to hard to learn on .If you can trust the gun to be repeatable over the coarse of a weekend's shooting match then it is a bunch easier to learn what u don't understand about the flags and more importantly the gun handling ..JR..Jeff Rogers..ps wind drift seemed to be about the same ,mabye infront a bit for the 175 ,but i would say just about to a man ,everybody in my area has sold off thier pointy bullets to the F/ class guys ,problem solved ..
Actually, this lines up perfectly with what I would expect based on the BC's.

Bruce didn't ask for the BC of 168 SMK, but I measured it at 0.567 which is significantly higher than what Sierra advertises. Now it's hard to model your test exactly because you didn't provide velocity data. However, the following is a likely scenario...

You're probably getting about 2850 fps from the 175's with 50.5 gr H4350. According to my calculations (using my measured BC values): in order to impact 9.0" above the 175's, the 168's would require a muzzle velocity of 2975 fps. This is likely near the velocity you were getting with 51.5 gr of H4350. In other words, according to the BC's I measured, and the difference in vertical impact that you observed, the 168's were likely going about 125 fps faster than the 175's, which is very believable.

Too bad you don't have any velocity data for those tests. Given MV, we could make a truly meaningful comparison.

By the way, the 168's at 2975 fps have 71.5" of wind drift (10 mph wind @ 1k yds) and the 175's have 71.9", so they're practically equal in terms of wind drift.

When I stated in my previous post that the heavier bullets always beats the lighter bullets in the wind, the 'assumption' was that equal powder charges were used. I'm still surprised that the 168's are so close to the 175's, even with 1.0 grain more powder.

I have to commend you on a successful test. Anytime you're 'chump' groups average 6.5", you're not doing too bad! Sounds like you got your equipment developed very well. How many shots were these groups?

-Bryan

Tony Z
02-28-2008, 09:44 AM
My apologies to J Valentine. I was not taking a swipe at you or your post and i did note that you stated as advertised BCs. What i was taking a swipe at was the highly inflated BC for the 168 Berger.
Brian, from our very agricultural methods, compared to yours, we have long felt the 168 SMK had a BC of around .550. I have shot the 168 Berger head to head at long range against the 168 SMK and i found very little between them in trajectory and wind drift. Because of the Bergers cost and difficulty in aquisition here in Aus, i stayed with the SMKs for years. I am suprised to see you give the Berger 168 a .617 BC so maybe its time for me to try them again.

Tony Z.

b moulds
02-29-2008, 04:00 AM
thank you all for your help. nothing beats experience.
one thing i have found is that it is easy to establish good loads for 600. some of these will be good at 300, & some won't. to get one which is good at 1000 can be very hard.
another thing i have found is that wind drift is a product of b.c. and velocity, which is why i am interested in the 162 amax. in the moderate capacity 284 win case the lighter bullet might have merit.
it also seems as though the old 168 sierra might be worth trying. i have always thought this bullet looked to have a higher b.c. than advertised.
with regards b.c.in general, isuspect that the slowest twist that will stableise the bullet at the muzzle will give the bullet a higher b.c. than a faster twist, due to a lesser ammount of precession & nutation. this puts longer bullets at a slight disadvantage with their faster twists.
regards,
bruce.

Doug Rumbaugh
02-29-2008, 07:16 PM
I have shot the 162 AMAX for about 5 years at long range on varmints and have found the .625 BC to be accurate when using the JBM web site calculations. I have shot over 2500 of them at random range targets from 650 to 1300 yards; most of the shots were beyond 1000 yards. The velocities I shoot are between 3200 fps to 3375 fps depending on the rifle and temperature. I chronograph the load, generate a chart from the JBM web site and go to the field. I have had amazing success with the predicted clicks. Also, at these velocities, the 162 AMAX is perfect for groundhogs at long range.

I have not used these bullets in competition but hope to this year. For hunting, you have to sort by bearing surface but I think that is true for all the others mentioned.

bsl135
02-29-2008, 08:26 PM
Bruce,
I would still advise in favor of the heavier bullet if wind drift is your biggest concern. For a given level of pressure, the heavier bullets may start out slower, but in the long run, they will have less wind drift at long range. Of course it's also important to consider the grouping potential of the bullets. I'm only talking about the ballistics.
Choosing the slowest twist that's adequate for stability is generally a good idea, but it's got little to do with BC. For properly stabilized bullets, the normal levels of precession/nutation that occur are so small (less than 0.1 degrees) that they don't affect BC a measurable amount. The same can be said of # and configuration of riflings. By choosing the slowest twist that stabilizes a bullet, you're minimizing the dispersion factors that are related to spin rate like bullet imbalance and in-bore yaw. In other words, not 'overspinning' the bullets can potentially help with grouping ability, but has nothing to do with BC. The exception to this statement is if the twist is too slow and the bullets are not adequately stabilized. BC can certainly suffer than.

Doug,
I'd like to discuss your observations of the 162 Amax fired in field conditions.

First of all, I have no interest in disputing your observations. I simply wish to illuminate some of the sensitivities that are involved in this kind of analysis (BC analysis).

When high BC bullets like the 162 Amax are fired at the high speeds you're talking about (3200fps+), the drop is quite insensitive to BC. In other words, you might have a relatively big difference in BC and it won't necessarily result in big differences in drop. For example, when I run the JBM program out to 1000 yards using the advertised BC (.625) and compare it to my measured BC (.580), both with 3200 fps muzzle velocity, there is only 9" difference in drop at 1000 yards.

I believe you when you say that you get accurate tables when you use BC=.625. But would you really notice if your tables were off by 9" at 1000 yards?

Here's another example. A common practice is to enter the measured muzzle velocity into the program as the actual muzzle velocity. This introduces error into the calculation due to the bullet slowing down between the muzzle and the chronograph. If you entered 3200 fps as the muzzle velocity, and your muzzle velocity was really 3210, and you used .625 for the BC, now there's only 7" error in your tables. Would you notice that?

You mentioned that you prepared the tables ahead of time and carried them out into the field. This makes it impossible to guarantee that your drop table is perfectly suited for the atmospheric conditions of that shot. If you prepared your drop tables assuming some set of atmospheric conditions, but the conditions were slightly different, you could easily introduce some error into your shot that could make it look like the BC is higher than it actually was.

Finally, you indicated that you adjusted your scope for elevation adjustments (as most LR hunters do). We all know that scopes, no matter now much you pay for them, can't guarantee perfect 1/4 MOA clicks for the full range of adjustment. This is yet another source of error that could introduce error into your assessment of a BC.

I really don't mean to pick on you. I believe you're a successful LR hunter because you know your stuff. I'm just saying that there are many reasons why our observations wouldn't necessarily agree. The shooting I did was done specifically to determine BC. None of the variables listed above introduced error in my test. Your purpose in shooting was LR hunting, in which there are far more variables involved that muddy the waters, and you might not notice it if your tables were off by such a small amount. In terms of drop, there's really not that much difference between a .580 BC projectile and a .625 BC projectile at high speed.

By the way, here's another interesting fact...

Myself and others are always on the 'G7 soapbox'. We say that the G7 BC is better for long range projectiles, blah blah blah.

Here's another example of why.

The tables that work so well for Doug use a G1BC of .625, and result in 21.2 MOA of drop at 1000 yards when fired at 3200 fps in standard atmospheric conditions. Using my measured G1 BC of .580, the program predicts 22.1 MOA of drop in the same conditions, which is a 0.9 MOA difference. Now, if you use the G7 BC that I measured, which is .297, the program predicts 21.7 MOA of drop, which is only 0.5 MOA different than the table that Doug generates using the G1BC of .625!

What this suggests is that the G7 BC is better able negotiate the large velocity drops that are common in long range shooting. When using a G1 BC, you have to have several BC's for different velocity bands, or have an average that's suited to a particular range shot. With the G7 BC, you don't have to worry about the velocity, the G7 BC stays constant and results in more accurate predictions be it drop, wind drift, tof, etc.

In conclusion, I don't think we (Doug and I) necessarily disagree about the BC of this bullet. In light of the above variables, I don't think you can fairly say that I'm underselling the BC of the bullet because the difference in drop (which is your measure of BC) is very small, and is affected by many other variables.

Again, my intent is not to say "I'm right and you're wrong". I think we're likely in close agreement.

-Bryan

b moulds
03-01-2008, 02:50 AM
the reason i am researching this subject is that when i shoot out my current 6.5/284 barrel, i will screw a 284 barrel in the rifle.
being very familiar with 6.5 bullets, i would find it very useful in understanding your 7mm b.c. figures, if you could offer figures derived in a similar fashion for 6.5mm 140 berger
130 berger
142 sierra
139 lapua
i am familiar with these bullets (8 barrels), so anything you can offer on them will give me something of a juxtaposition which is meaningful.
in 6.5 i have gained best group elevations with 140 bergers, but they do require keeping in touch with as the throat moves forward.
regards,
bruce.

bsl135
03-01-2008, 08:41 AM
Sorry Bruce,
I have not tested any 6.5mm bullets yet. Actually I have, but my sensors failed so the tests were invalid. I'll try to remember you when I do test that caliber again, but it might be a while.


when i shoot out my current 6.5/284 barrel, i will screw a 284 barrel in the rifle.

I'm very familiar with this sentiment! Here's the article (http://www.6mmbr.com/gunweek053.html) that gave me the information I needed to make the decision to go to the straight .284. I don't know Jerry personally, but we've corresponded on many topics and I consider him a top shooter with a lot of valuable advice to share. For someone considering the .284, this article is a must read.

Good luck,
-Bryan

Doug Rumbaugh
03-01-2008, 12:23 PM
Bryan,

I am not a ballistic expert all I know is what I observe in the field shooting at small bottles and varmints at long range. I have tried to use published BCs for many types of bullets to calculate charts for my friends and they almost always have to be adjusted to get things to work out. In my experience, the one standout bullet I have tried is the 162 AMAX.

I was never happy with the charts I calculated off the web so I always modified them in Excel to give me the format I liked. It took some time so I made up charts at the temperature I usually shoot at, 70 degrees. Over time, I made up charts for velocities of 3200 fps to 3375 in 25 fps increments. I chronograph my load, zero the rifle and go to the field. I pick the chart that best matches my chronographed load and my extreme velocity spread is usually between 15 and 25 fps. I set the chronograph (Oehler w/ 6 foot spacing) 10 feet in front of the gun and enter that into the JBM program.

When I get to the field and start shooting, I may pick the next higher or lower chart based on observed hits. I used to think it was because of velocity variations but now I am pretty sure it is also because of temperature changes. Basically at 1000 yards, with my setup, a 12 fps difference is the same as a 10 degree difference and is 1.7 inches. I am usually within a click or two at 1000 yards. Using the .58 BC, I would be consistantly 4 clicks off. Again, I cannot explain why my field experience differs from your ballistics testing. Maybe it is something else I am doing. I really don't mess with atmospheric pressure so maybe that is it.

I tried the Berger 180s once using the same methods I used to verify the AMAXs. I shot at 1 qt plastic oil containers at 700, 800, 900, 1000 and 1100 yards. Using the 7 STW, which I was getting 3200 fps for the AMAX, I could only get 2900 fps with the Berger. Interestingly enough, the 100 yard zero was very close. Anyway, I shot at the same bottle group (1000 yards) with the Berger 180 setting and shot 5 feet over it. That convinced me the 162 was the way to go. When I got back and analyzed the results, I got almost the same BC of .64 for the Berger. Considering the 350 fps velocity difference no wonder the AMAX was so much flatter.

As an aside, I noted similar results when comparing the 75 AMAX and the 80 AMAX in my 220 Jaybird. The heavier, higher BC bullet could not be pushed anywhere near the velocity needed to be flatter than the lighter one.

Since I have now integrated the JBM DLL into Excel and can generate my charts with great ease and speed, I now have a whole notebook of charts in 25 fps increments and 5 degree increments. Looks pretty silly but I leave all but a couple in the truck.

You asked if I can distinguish 9 inches when shooting? My answer would be yes. I shoot from a bench with a 1000 yard BR capable 18 pound rifle w/ a muzzle break using my 1000 yard BR rest. My scope is a Leupold Premier boosted 20-50 power scope w/ a custom reticle. I usually have a partner spotting who has decades of experience doing it with top of the line optics.

The shot answer is I am stumped. I believe your ballistics experimentation says .58 but for me, there is no way you can convince me that my .625 number is wrong. Just last fall getting ready for deer season, I set up some 2.5 gallon water filled bottles to test the expansion of a friends 260 grain .375 bullet out of a 375/408 Cheytac. As a joke, I set up a couple 2"/2" cube bottles that had some sugar drink my kids had. Anyway, after blowing up the big bottles with the Cheytac my friend told be to shoot the little bottle I had at 1000 yards. I had done my zero/chrono dance just before we left so I the rifle was fouled and ready to go. I got it out, picked the correct chart for the temperature, set the clicks and hit the little thing dead center with the first shot. Lucky shot, true, but if my BC was really .58 instead of .625, there is no way I would have hit it.

I now have my calculations on my notebook computer and have purchased a Kestrel 4500 for all the atmospheric data so this year I will do calculations in the field. Maybe I will figure it out that way.

In the BR world, it doesn't really matter because you have plenty of sighters to get zeroed and the rest is how fast you shoot and how accurate your rifle is. Hunting is a different story, random distance targets with no sighters. Typically the calibers and bullets used are totally different. Anyone interested in long range varminting, I highly recommend the 162 AMAX in a 7 STW/7x68 Imp/7 Boo Boo or something similar. The bullets start failing at like 3400 fps so a 7 UltraMag is a bit too strong.

I am more than willing to accept I am wrong in some way but whatever I am doing seems to work for me. If this info is of use to someone, cool. Sorry about the long post.

Tod Soeby
03-01-2008, 01:02 PM
Doug,

You just took a MONSTER leap forward when you bought the Kestrel 4500 and a pocket PC. Those of you with ballistic programs should "play" with altitude, barometric PSI, temp, ect.....numbers. That perfect cool, cloudy, overcast day with no mirage(28.XX) that you sighted in at is a completely different animal at LR than that bright sunny day (31+)!!!

You need to have the current conditions at your fingertips in the field when there are no sighter's!

AGAIN, JUST MY .02
TOD