weighing VS throwing powder

[mks]

What I meant was taken from the context of working up multiple loads with small samples. In chronographing ammunition, typically there are not enough rounds fired to get ES's wide enough and still let SD remain low. So, someone working up loads with several different combinations will see the ES and SD correlate and go in same directions. However, if you were to pick one of those loads and shoot a thousand rounds of it, yes, you could see high ES and low SD. But not always.
Also, in chronographing ammunition (working with relatively small samples compared to some other calculations), the only time I have ever seen the ES = SD was when they were zero. But that hasn't happened very much!


I always write down the ES and SD for each load I try. BUt if I could only have one of them, I'd take SD for sure.

Yep, that's pretty much what I do, too. It seems like SD settles down (asymptotes) faster than ES as you shoot more rounds, since it is based on all shots rather than just two. This agrees with theory, since SD has an asymptote, but ES just keeps getting bigger.

 

[K Hope]

To get SDs of any real quality, for a number of loads, requires sample sizes that are larger than I am willing to collect, given the cost per shot, counting barrel wear. Also, I do virtually all of my shooting at 100yd., a distance that does not put as much of a premium on extreme uniformity of velocities. This is why I don't do much chronographing. On the other hand, since there is some thought that velocity can be correlated to accuracy nodes, I find it useful to know the velocities at which these nodes occur, so that I can find them more easily when I make a component change. Obviously this situation would be a lot different if I were shooting at longer ranges. This does not mean that I don't pay attention to things that are known to contribute to consistency in velocity. I do. It is just that my primary reference is group size.

Boyd, Real solid post I like it.

I think the premium’s you mention are actually quite high when looked at from an internal ballistic view rather than one solely based on velocity, short range / long range (sorry if I miss read your post); mostly attributed to by the chamber pressure at a given velocity of the initial burn rate. The part that I do not agree with Al on is that he believes these values to be predominantly linear based on weight and best metering.

I think there are very few people who have the time, money or energy for this amount of testing; just too many variables.


Ken

 

[Boyd Allen]

MKS,

As I am drinking my first morning cup I have reviewed the information that I posted links to, and the example that you gave. Thanks you for your patience, and the further clarification. Of course you are right. The first sentence in my previous post is incorrect. I did the calculations.

Thank you for taking the time.

Boyd

K Hope,

 

[K Hope]

Volume is my friend

Interestingly enough, I always assumed spherical (ball) powder metered best........ until I had opportunity to load up several hundred rounds using 6 different ball powders.

Turns out I was wrong. IME it doesn't meter as well as "square" extruded powder.

I hope someone else takes the time to test this,
al

Al, it’s powder it is all about bulk density. You cannot wish volume away.


“A bulky powder (occupies more powder space) measures more uniformly, because normal variation in the measured volume represents a smaller percentage of the charge weight.” (Ed Harris)


Ken

 

[alinwa]

Al, it’s powder it is all about bulk density. You cannot wish volume away.


“A bulky powder (occupies more powder space) measures more uniformly, because normal variation in the measured volume represents a smaller percentage of the charge weight.” (Ed Harris)


Ken

I have no idea what you're saying.

Do you routinely achieve single digit ES?
al

 

[K Hope]

Al, I do not doubt your testing results or that lower ES are not beneficial; I am saying that the information supports your test results.

I shoot score and group; for score I preload and I am acutely aware of the advantages of doing so. H4198 in this case permits me to do so. I would like to be able to do this with group but do not feel confident doing so because of n-133’s temperature sensitivity. At the smaller shoots I attend even when throwing powder I have a hard time keeping up timewise. Loading to your tolerances at the shoot in order to keep these benefits, for me, is not possible.

Short answer to your question is that my chronograph sits on the shelf collecting dust. At my level and for all the shooting that I do, the bigger values - for me - are more effectively managed using POI.

Ken

 

[Scott Fletcher]

Gentlemen:

The attached is why I measure powder of all loads at all distances. The 2nd sheet identifies the particulars about the rifle used. I used a Hart Accuracey Asset to turn my hunting rifle into a "bench" rifle. Bullets were either 52 grn moly coated match Bergers or 55 grn Hornady moly coated V-max's straight from the box. I have no idea what the seating depth was, but I suspect it was around 0.025 off the lands. (these targets were shot over 10 years ago before I became "enlightened" about the importance of seating depth) Charges were weighed with an RCBS electronic scale of the period ($200 or so). I have no idea what the model number was, as I inadvertently toasted it one day and pitched it into the round file.

The top target (1st sheet of 6 smaller targets) shows what happens to a "bughole", 5 shot group with a 0.1 grain incremntal powder increase. I always chrono everything I shoot (Oehler 35P), but can't find the assocciated data sheet. However, target #6 shows what can happen with an obviously "different" velocity. I have no idea why there was a 250 fps bust, other than "operator error" (ya gotta pay attention to the winkin' blinkin' lights)

The bottom target (2nd, lower sheet) shows what happens with 3-shot groups with a 0.3 grain incremental powder increase. (I'll get to the significance of that powder increment directly) There are two items of note:

1) the 3 shot groups really aren't that bad considering my skill level and equipment. I have no idea how a true short range benchrester would asses some of them in deciding whether or not to keep the load and use it in a match, but targets 4, 5, and 6 look pretty good to me.

2) notice how the center of the group significantly shifts around based on powder charge. The most noticeable shift also occurs among targets 4, 5, and 6, the ones indicative of "the" load. Now consider what any group would look like if there was a 0.3 grain bust (say from 35.7 to 36.0, or 36.0 to 36.3) in the powder weight. Poster child ugly.... (typically associated with most of my range efforts)

I have a Harrell measure. At the time, my typical "extreme spread" of powder measuring was (you guessed it) 0.3 grains, no matter how much "bumpin', grindin" and holdin' ma jaw right". I believe static electricity is the primary culprit in preventing consistent powder throwing. (when kernels adhere to the case mouth, "cosmic forces" are involved )

For short range (200 yards or less), I believe velocity variations (however anyone wants to portray them) are sidebar issues. Boyd Allen had what I believe is an an excellent point: what is the "pulse" in the system, in terms of velocity, that produces the best accuracy? Knowing that velocity is very beneficial in recapturing accuracy when components change.

I have no experience with a 6 PPC. However, I have done considerable testing with other cases trying to identify powders that the system "likes". I do this by loading 5 cases of a selected powder at 1.0 grain increments (that's correct, no typo, mine's bigger than yours.... ) with bullets just touching the lands. I then shoot all 5 at one target at 100 yards to see how they "group". The powder associated with the preferred group then gets selected for actual load development. I've had one instance where a 5 grain powder weight spread produced a group in the 2's. I've had several in the 3's, and, as you can imagine, a good many of them had measurements associated with that nefarious oriental fellow Yu Flung Dung. The point is that there are some systems, coupled with a specific case, that seem to fall in love with a particular powder and primer combination. I suspect that the 6 PPC is very forgiving in that regard....up to a point. Otherwise the short range bunch wouldn't be moving heaven and earth to buy 14 tons of some esoteric powder produced only on February 30th. If you should happen to be stuck with a powder that your system tends to tolerate instead of "like", then weighing powder, as indicated by the attachment, could become a key step for achieving consistent, competitive accuracy.

For those of you wondering "who in blazes is Scott Fletcher?", I am an infidel 1000 yard benchrester. "It's the same.....only differnet"

Scott

 

[Boyd Allen]

Scott,
Years back, I determined that most rifles that have sporter or varmint stocks do not do their best work with the front bag positioned where the Hart Accuracy Asset requires it to be. My guess is that this is because of stock flex, and the attendant vibration patterns. In every case that I can remember, rifles shot much better with the front bag no more than 2-3 inches in front of the action. Based on my experience with HS precision stocks, they may be even less stiff than a wood stock of similar shape. As far as the importance of a tenth of a grain goes, I have seen much less difference than your target shows with my 6PPC bench rifle, or even my varmint rifles, resting them farther back on their forends. It may be that with all of the other care that you have obviously taken, that you have a basic stock and sand bag issue that has made your results more extreme than they otherwise might be. Also, I have a question. Were the groups shot over flags, and what were the conditions like?
Boyd

 

[alinwa]

To eliminate the static charges you must ground the thrower. My throwers have 10ft of light wire attached to them. Also, wipe the powder reservoirs with used dryer sheets, 'Bounce' or the equivalent.

BTW I ground everything, scales, throwers, ChargeMaster.......

hth


al

 

[virg]

For short range bench rest, powder weight differences within a reasonable degree, paid little effect on accuracy. Well proven by Virgil King in the Houston warehouse.

Three major things count to end up in the winners circle provided equipment quality is equal (which it usually is):

!. Barrel quality
2. Bullet
3. Shooters ability to read conditions.

That's it.....

 

[Scott Fletcher]

Gents:

The last thing I want to do is cause heart burn or kill sacred animals. I speak as a successful competitor. As such, I admire and respect the "fire in the belly" of folks who want to improve/do well at matches. It is my time to "give back" to the sport. The only reason I post is to help competitors, not fuel esoteric debate. What I discuss/present has worked for me in competiton. Those of you who are competitiors must decide for yourselves if what I have to say deserves your consideration. Take the best and leave the rest.

I do my load development for 1000 yard competition at 200 yards. I hope everyone will agree that 200 yards is "short range". With 240 grain Sierra's, ligtht gun (17 lb) 3-shot groups went from 0.766 to 0.396 to 0.186 with an incremental 0.1 grain increase in powder. (case basically a 300 Win with powder on the order of 70 grains) The result showed up on paper at 1000 yards this December (see attached) I have several other examples where "garbage turned to gold" with a 0.1 grain change in powder charge in cases containing from 50 to over 100 grains of powder.

The cases in question are not a 6 PPC. A question that rightfully should be asked: "Is this concept of precision powder determination applicable for 6 PPC when it appears to be applicable in other cases/chamberings?" I think the answer lies in the degree of precision in which the groups are evaluated. I sweat 0.1 inch in my groups at 200 yds. With the inherent accuracy of a 6 PPC, I would be sweating groups to the nearest 0.010 at 100 yards, and using 200 yd groups as the final culling criterion. Because the 6 PPC is so accurate,you may not be able to see the effect of 0.1 grain on groups at 100 yds, but I'm inclined to bet the ranch that you can at 200 (totally independent of velocity variations). After all, how many instances are there in short range competiton where the difference between 1st and 2nd is measured in thousandths of an inch? Will those thousandths of an inch show up at 100 yards because you sweated the load at 200? All I can say is that if I were shooting short range with a 6 PPC, I would want to be damn sure that I wasn't beaten by my load, and results at 200 yds would be my litmus test.

From a pragmatic perspective, another question that could be asked is: "Will weighing powder charges hurt my groups?" I think not. The final question is: "Will weighing my powder help my groups?" There is only one way to find out....

Based on what I have seen in my load development, the powder, primer, and bullet seating depth can have a significant effect on what shows up on the target, independent of barrel and bullet. That is a whole different topic that I alluded to in my previous post. Are these concept also applicable for 6 PPC? If I were shooting short range, I would proceed with my load development assuming that they were. How could it hurt?

Scott

 

[Boyd Allen]

I t couldn't...There are a fair number of Chargemasters at short range matches, but they don't always win. If you look at recent records, there are a significant number that were shot with thrown charges.

 

[Scott Fletcher]

Hello Boyd:

"Always" is a tough word in any context. There tend to be exceptions to vitually everything except death and taxes. I am interested playing the percentages, the "more likely than not" scenario's. Than will be the typical context in which I offer my experiences and what I have learned.

There is another aspect to my "advice", one that lots of folks may be thinking but have not yet articulated. No one has yet to say that weighing charges is "not practical". Practical is a subjective term, and reflects personal preferences, skill sets, and finances, all valid parameters for the individual. Only the individual competitor can assess these issues and their interlationships, then arrive at an approach that is best for them, hopefully with full understanding of potential benefit.

I am an engineer. I am concept based. I will try to portray what I believe are the concepts involved and the reasons involved in my solutions. My solutions are not absolute, by any means. As the saying goes, there is more than one way to skin a cat. By understanding the concepts, folks are better equipped to make informed decisions, potentially substituting an approach better suited to their sense of "practicaliy" or "precision".

I'm glad you responded, cause I owe you an answer: "Yes, I used wind flags". The jury is still out on whether or not I am fully capable of understanding what those contraptions are trying to tell me, let alone make decisions about when to actually pull the trigger. Most short range folks wouuld undoubtedly blister my backside with their painfully acquired wind reading skills.

There has been some lack of focus to my "advice", which is entirely my fault. To be succinct: the reason I believe it is beneficial for short range benchrest folks to weigh powder charges is that I am convinced, through over a decade of load development involving 17 different chamberings/bullet combinations, that significantly better 200 yard groups will be obtained. If better 200 yard groups are obtained, better 100 yard groups will also be obtained.

Even with my relatively crude chamberings (in comparison with the accuracy potential of the 6 PPC), groups at 100 yds don't really tell me how good my load is. That statement is made in the context of me having to compete with my chamberings and bullets in a short range match with all my competitors shooting 6 PPC. In preparing for such a short range match (max yardage at 200 yds) my benchmark groups to evaluate my load would be at 200 yds. The reason I focus on 200 yd results is that this is the first yardage where I can trully assess the group's shape. I am looking for "round", with any "out of round" oriented horizontally, keyed to a wind condition that I didn't heed. Vertical dispersion tends to indicate a slight increase or slight decrease in powder charge is warranted, or the seating depth needs to be adjusted 0.001, typically toward the lands. In some instances, a primer change or neck tension change gets the group "round". Vertical at 200 translates to vertical at 100, with the resultant penalty of lost thousandths of an inch (100 yd targets) to hundreths (tenths?) of and inch (200 yd targets) that could mean a place or three in the final standings.

The 6 PPC is so accurate that there is no way that I can truthfully say that I could intellegently evalute a PPC load at 100 yds, unless it wasn't round. If I owned a 6 PPC, I would briefly tinker at 100 yds to "get the crude out", then focus on what the load was trying to say at 200 yds. All load adjustments/modifications would be evaluated/proofed at 200 yds. I would obtain chrono data as I progressed, only to understand what effects temperature and humidity had on my velocity/groups. Such data would be used for strategic adjustments at matches based on expected/actual temperature and humidity values. (this approach is essentially what I do now, except I rarely do group testing at 100 yds any more)

My range conducts NBRSA affiliated short range matches. I cannot recall any instance where I saw my short range colleagues practicing/working on load development at 200 yds. Is this a hidden agenda/real issue item? Don't know.

The intent of this post is to present concepts that I believe are applicable for improving match results. If folks believe any or all have merit, I believe there will be a positive result. If folks believe none have merit, then that is a positive result as well. Every once in a while it's good to reaffirm "these truths to be self evident".

Scott

 

[sdean]

Scott you seem to take it for granted that the best load for 200 is the best for 100. I have found that it not always the case.

Stephen

 

[Scott Fletcher]

Hello Stephen:

Yes, there exceptions to everything. As I said, I am in to "more likely than not". Even in "my world" of long range, there are credible fellows who have kept out of the sippin' whiskey long enough to tell of loads not shooting at 200 yds, but absolutely hammering a 1000 yd target. It happens, but not very often. A tip of the cap to you for knowing your system, and thoroughly frisking it for its "best".

Scott

 

[alinwa]

Actually, IMO a load can only be tuned for one yardage.

 

[alinwa]

This is a pretty common way to tune, tuning at 200 for both yardages. And if one had to choose 1 yardage to tune at, it's the best choice.

 

[JRB]

Is this the real question?

After a long read and I am still not sure if i understand all that is said? or implied, i have one question.
It seems that at distances of 200 yds the powder can be weighed to .1gn or hopefully less, and the powder being throwed can be delivered to .2gn if you are well practised. Now i am chosing these perameters because most do not have the most expensive scales available to qualify the results exactly, but this is not my point.
What my question is quite simply,
Given that one can acheive a powder drop of .2gn variation or better.
How much of a powder variation do you need to effect the 'Tune'? or ES for that matter?
Jim

 

[Al Nyhus]

My question is quite simply,
Given that one can achieve a powder drop of .2gn variation or better.
How much of a powder variation do you need to effect the 'Tune'? or ES for that matter?
Jim

Jim, it depends. Some combinations have a wider tune window than others. You have to consider the combination the as entire gun not just the cartridge it's chambered for.

ES, in and of itself, has never been a solely reliable indicator of a trust worthy tune in my testing. What the muzzle is doing as the bullet exits has a far greater influence than ES. If the muzzle is pretty 'flat' and calmed down as the bullet exits, the ES is pretty meaningless. If the muzzle is in motion, an ES of 1 can still give you be crappy groups and/or a sensitive tune....regardless of how accurate the powder weight.

Good shootin'. -Al

 

[Pete Wass]

Muzzle Blast:

I have a friend who is by profession an engineer and by avocation a "shooting Nut" . In our conversations, he has mentioned muzzle blast, or the instability of, as being a culprit for poor accuracy. His contention is an unstable muzzle blast and/or bad crown will cause bullets to become unstable and "cone", I think the term might be. Why or how the muzzle blast becomes more stable with various loads is a situation I can't seem to wrap my feble mind around though. Any ideas on this theory?