brass weight sorting

[rscott5028]

fact: 2 cases can weigh the same and have different volume

fact: 2 cases can weigh different and have the same volume

Neither condition is perfect.

If all cases weigh the same, have the same volume, and are of the same shape and other physical properties, then you're on to something.

I believe weight and volume are more often related than not (for fired brass). And, volume is a bigger concern. But, it's also more cumbersome to measure than weight.

The amount of effort you put into case prep and sorting is a choice you make.

There are some things you can control and some you can't. So, you might as well do all you can before you squeeze the trigger.

Now... if you're flat worn out due to OCD case prep and are never in the mood to practice, then you may have defeated yourself.

So, my aim is to have a method of procedure that's sustainable, repeatable, and sensible for the type of shooting I'm doing.

-- richard

 

[rscott5028]

Has/does anyone track brass performance down to the individual case level?

I just track by batch # because they get jumbled when cleaning.

If weight is a mediocre predictor of volume.
And, volume is a good predictor of MV.

Isn't past MV your best predictor of future MV assuming consistent treatment and all other variables held constant?

I assume you'd want to disregard the 1st firing of new cases.

But, do cases perform consistently with relative MV from 2nd to 3rd to 4th firings?

If not, then why not?

-- richard

 

[LouBoyd]

Has/does anyone track brass performance down to the individual case level?

Some benchrest shooters do, or at least have tried to see what results can be achieved. Some even tried shooting each cartridge with the same roatational angle and noted the position of each impact to try to duplicate each shot. Some have reported some success. Top bench shooters pay a lot of attenetion to barrel performance and to consistancy in doing everything the same for each shot. For example, the time a cartridge sits in the rifles chamber or how long it sits in the sun before it's chambered will affect velocity too. So will the residue left in the barrel from previous shots.

There are lots of factors in achieving better accuracy. I think ti's worth applying my efforts where they'll do the most good in overall performance. Not all shooting is the same. What gives accuraracy with 25 yard pistol, 100 and 200 yard behchrest, 1000 yard benchrest, and variable distance long range hunting have some similarities but also a lot of differences. Each of us only has a finite amout of time to apply to our shooting. That can vary a lot from person to person.

Bryan Litz's book "Applied Ballistics for Long Range Shooitng" has a good section on how various error souces combine. It's good reading for any shooter but partiularly for long range hunting.. Unlike target shooters, first shot cold barrel shots are far more important for hunters and far more difficult to achieve than punching small groups after you've gotten on target with a couple of sighter shots. In damp weather with soft soil there are no dust puffs to tell where your misses impact. When the first shot miss all you know is that it wasn't done right often with no clue how to correct it.

My point is that for hunting, buying or building a rifle and ammo which does not requre extaordinay effort is practical to achive the situation where enviromental factors, usually wind, overwhelm the launch angle or velocity dispersion errors. It makes sense to put your effort both in equipment and personal training where it will do the most good. Reading and comprehending Brian's book is a good use of time for a few hours to understand the effects of range estimation, wind estimation, and ammo variablity. Practicing target shooting in field conditions, particularly learning to estimate wind and wind deflection, is more likley to result in hunting success than loading bechrest quality ammo. Practicing stalking is very worthwhile. Taking shots at game beyond one's capabilities is not what long range hunting is about.

 

[Reloader222]

The arguements may be all valid but what is the results?......

Is there perhaps somebody who did some testing with variables in case weight and the impact on groupings? For instance:

95grain cases 3 shots = grouping size ....

96grain cases 3 shots = grouping size ....

97 grain cases 3 shots = grouping size ...

AND ....

ONE 95GRAIN, ONE 96GRAIN AND ONE 97 GRAIN CASE = GROUING SIZE ....



AND IN EXAMPLE:

50 grain water capacity 3 shots = grouping size ....

51 grain water capacity 3 shots = grouping size ....

52 grain water capacity 3 shots = grouping size ....

AND

ONE 50 GRAIN, ONE 51 GRAIN AND ONE 52GRAIN CAPACITY = GROUP SIZE ....

 

[Mikecr]

I think you should do that testing Reloader222.
And I think you should test to see if it HURTS anything to match cases by volume.

I believe alot of folklore(and laziness) w/regard to capacity testing has poured out of the point blank BR shooters, who would be least affected by moderate volume variances, yet very easily spot obvious offenders by weight and range flyers. Afterall their tiny cases(6ppc) amount to 223AI capacity, and they run extreme pressure loads that work around affects of common capacity variances. This is why they can shoot incredible groups while not even measuring powder weight.
But all that's a different world from hunting cartridges.

I promise it won't hurt any of you a bit to check your capacities.

 

[Reloader222]

Mikecr, I have loaded my groups of case as follow:

1) Same Weight
2) Variable Weight
3) Same volume
4) Variable volume

I am going to test it this week.

 

[Mikecr]

That's great Reloader222.
Also, be sure to log weight-vs-volume, and qualify the method and condition of volume and weight variances for your test loads.
Before testing, take your gun to it's baseline with prefoulers and warmups that measure as expected across a chronograph.

Ya see, you have to actually isolate, identify and correlate, the variances from each other. Else capacity variances might actually be initial loaded volume differences, rather than actual case capacity variance. While this would probably affect change, it isn't the same change.
Your case preps would need to be taken to standard as well. If for example, you 'cause' weight and/or volume variances by changing trim length, then all results could be compromised.

Not to discourage your testing, this is a good endeavor on your part.
Just reminders, as the results would & should be challenged regardless of implication.
Keep us posted

 

[Reloader222]

Thanks Mikecr

I have tried my best to do it right:

All cases trimmed and necks turned. Unfortunately I do not have a cronograph to measure velocity, this round it would only to verify impact on groupings. All primer pockets were unified. All flash holes has been deburred. Al case necks were polished with steal wool on an old cleaning brush.

The calibre is .222 Remington. I have used CCI Benchrest4 primers and weight each load on my RCBS 5-10 scale. All bullets weight individually and exactly the same weight (55gr Hornady Varmiter).

I have made 4 batches of 3 shots:

1) Same Weight: 3 Lapua cases weight 108.8gr
2) Different Weight: one 93.8gr, one 95.0gr and one 101.8gr (cases Norma/Sako/PMP
3) Same Volume: 3 Norma cases: Volume of all 3 are 26gr water weight
4) Different Volume (water weight): one 23.6gr,one 25.2gr, one 26gr (cases Norma, Lapua and PMP)

The shooting range is underground and there is no wind involved -100meters. I will shoot the groups on Friday for temperature reasons. Temparature would then be around 25 degrees Celcius.

Thanks for your advise - I will keep you posted on the results.

 

[rscott5028]

Thanks Mikecr

I have tried my best to do it right:

All cases trimmed and necks turned. Unfortunately I do not have a cronograph to measure velocity, this round it would only to verify impact on groupings. All primer pockets were unified. All flash holes has been deburred. Al case necks were polished with steal wool on an old cleaning brush.

The calibre is .222 Remington. I have used CCI Benchrest4 primers and weight each load on my RCBS 5-10 scale. All bullets weight individually and exactly the same weight (55gr Hornady Varmiter).

I have made 4 batches of 3 shots:

1) Same Weight: 3 Lapua cases weight 108.8gr
2) Different Weight: one 93.8gr, one 95.0gr and one 101.8gr (cases Norma/Sako/PMP
3) Same Volume: 3 Norma cases: Volume of all 3 are 26gr water weight
4) Different Volume (water weight): one 23.6gr,one 25.2gr, one 26gr (cases Norma, Lapua and PMP)

The shooting range is underground and there is no wind involved -100meters. I will shoot the groups on Friday for temperature reasons. Temparature would then be around 25 degrees Celcius.

Thanks for your advise - I will keep you posted on the results.

Some information is better than none and it may give you an indication of what to expect. But, unless the results are dramatic, then your sample sizes are far too small to be statistically significant.

Nonetheless, we look forward to the results.

-- richard

 

[nheninge]

Love the comment on stats Richard. Too much we rely on he said/she said. I'd love to see some real data with a good statistical design, controlled randomized variables, and valid conclusions drawn (complete with p-values) for the conditions tested under. Sure would eliminate a lot of the arguments. So many variables, so little time...

However, even these "little" trials provide a lot of good info to get you started

 

[Bart B]

I once shot two 15-shot test groups at 1000 yards with a .30-.338 Win. Mag. One group was with cases all exactly the same weight within 1/10th grain. The other 15 had a 5 grain spread; about 1% of their 235 grain or so case weight.

Both groups were fired with alternate shots; 1 with exact weight then one with high/low then 1 exact and so on. Did this to simulate what happens over 30 consecutive shots with each case weight type.

Both groups were about 6.5 inches in diameter; close enough to not make a difference. Shot dispersion in both were quite even. Both were horizontal from each other; bullet drop was the same.

Did the same test with a .308 Win. with a case weight of 171 abd 151 grain average weight. Same results; no difference in two 15-shot groups fired the same way.

So I'm convinced a 1% spread in case weight has virtually no effect on accuracy.

Talked with two primer company reps and they said there's a greater spread in accuracy between primers in a given lot than what a 1% spread in case weight has.

So, how does one sort primers as to which ones have the most uniform ignition properties?

 

[Boss Hoss]

Edited

 

[nheninge]

I'm no mathematician, but 1% of 235 grains is 2.3 grains.

 

[Bart B]

If you shoot that good you need to compete with that rifle in BR Matches!!

No way. I don't shoot accurate from a bench. The only way I do well is slung up prone on the ground with my front hand and stock toe on rice bags. I can usually hold under an inch of wobble area on a 1000 yard target.

Besides, I don't want to hurt the BR crowd's feelings by doing that well with a solid wood stocked Win. 70 conventionally epoxy bedded with new cases.

But I am pleased with how little money it took me to do that well....
$66 for a Model 70 post '64 .264 Win. Mag. barreled action.
$20 to lap the lugs then square up the bolt and receiver face.
$250 for a Kreiger barrel chambered and fitted.
$130 for a PJ Wright wood stock I hogged out and conventionally bedded myself with Devcon plastic steel, a fore end rail and butt pad. Smoothed the wood and finished with FullerPlast.
$110 for a used Weaver T20 scope with rings and a Davis 25 MOA sloped base.

Most folks spend way too much money for a very accurate rifle.