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brass weight sorting

 
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  #8  
Old 10-17-2011, 09:00 AM
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Re: brass weight sorting

Quote:
Originally Posted by Boss Hoss View Post
Well if that is your opinion then you are certainly entitled to it. Just because you do not have the means to accurately measure the internal volume that is a process issue that you must resolve. I myself was skeptical of this at first because I wanted an easy way to measure the interior volume of cases. My smith who is a HOF Shooter and has held world records in more than one discipline conducted extensive testing to determine if weighing cases was a valid method for determining volume using Lapua brass for his 6mm PPC and found that it was not.

My testing involved the use of Lapua brass made by Norma (300 win) and it confirmed this conclusion. You are right in that it is a time consuming and tedious process. If it makes you feel better and gives you more confidence at the line then by all means go ahead and do it.
Thanks BH.

I do have all of the nessary equipment and chemicals to treat the water (For the removal of
surface tension and demineralise the water) and laboratory testing instruments. And based my
opinion with apples to apples testing of both methods.

I totally agree that volume is the goal but the difference is marginal if not immeasurable if done
right and my recommendation has allways been to make the cases consistant no matter what the
process.

I would recomend that anyone interested in the best accuracy possible try both methods and
decide for them selves which one they want to use.

After all, there are more ways than one to do anything.

J E CUSTOM
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  #9  
Old 10-17-2011, 10:37 AM
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Re: brass weight sorting

Off center brass can weigh the same as centered brass. Banana Brass can weigh the same as straight brass. About the only time weight might mean anything at all is when its necessary to make good loads from cheap brass. I dont see any harm in weighing brass I just dont see that it can demonstrate anything useful to any one other than the 100yd extreme accuracy club. To demonstrate its usefulness to my satisfaction would require the use of a very long tunnel in the bottom of a salt mine.
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  #10  
Old 10-17-2011, 11:20 AM
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Re: brass weight sorting

Few things;
-Capacity does make a difference, and it can be seen across a chronograph.
-Until measuring capacity you can not know what the weight means, and therefore should not use weight alone as a basis of culling. SO YOU MIGHT AS WELL MEASURE IT.
-FL sizing does not improve capacity variance from fireformed/unsized cases, but degrades it from there.

Fireforming is a prerequisite.
Anyone who capacity checks cases should realize that it must be done with fully fireformed/unsized cases pulled from a smoking chamber. This is the most consistant they will ever be, and you want to see it at it's best before deciding on what stays or goes -based on capacity. You don't do it with new cases. You don't do it with sized cases.
Once you FL size cases, your capacity basis falls apart because you've changed it, and springback countered everywhere to leave variance -unrelated to the case volume..
Just as unrelated as weight...
Hell you could squish brass flat with a hammer, zero H20 capacity,, same weight!
Blow the shoulders forward for an extra 10gr capacity? SAME WEIGHT!

I measure capacity, and I'm sayin it's not a big deal. It's easy.
The ONLY downside to it, is that some fully prepped and fireformed cases will likely depart from the pack w/resp to capacity, and sadly they must go.
Well, ding dong they're gone, and then I don't have to worry about capacity mismatches.

Bottom line; you can find some problems weighing brass so it's not a bad thing to do.
But it is not a replacement for capacity measurements.
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  #11  
Old 10-17-2011, 06:11 PM
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Re: brass weight sorting

I agree with JE Custom in principle. I recently however ran calculations using Quickload to measure the effects of a 1 grain weight difference. The concept is that cartridge brass has a specific gravity of 8.56 compared to water with a specific gravity of 1.0. Therefore a case with 1 grain less brass increases the case capacity by 0.117 grains of H20. .

My calcuation assumed a 300 Win Mag shooting 190 grain Bergers at 1000 yards. I assumed SAAMI seating depth and 75 grains of VV-N560 powder ( a load I use) with a 24" barrel. The increase in case volume (in this example from 93.0 to 93.117 grains reduces the camber pressure and in this calculation dropped the velocity from 2959 to 2957 ftps. The calculated drop at 1000 yards (standard metro and sea level) changed from 311.7 inches to 312.2 inches. A difference of 0.5 inches.

Is a half inch at 1000 yards important? It could be the difference between winning or loosing a 1000 yard benchrest match. It could matter if you're shooting prairie dogs.

I also checked the effect of a 1 grain change in propellant weight. Going from 75 to 76 grains changed the velocity from 2957 fps to 2999 fps, a difference of 40 fps which changes the drop at 1000 yards by 9.5 inches. I think any long range hunter would agree that's significant.

Can brass weight vary without a proportional change in case volume? Yes. When brass is fired the case walls and neck conform to the chamber dimensions, but differences in the case head diameter or the volume of the extractor groove are not reflected in the interior chamber volume. If the weight difference is in the neck it can have other other effect which affect velocity and accuracy.
Neither sorting for weight uniformity or volume uniformity is a guarantee that the walls and necks are symmetrical.

For it to make sense to sort brass to 1 grain it should be obvious that one must also measure charge weights to 0.05 grains or better to make weighing cases have more effect than charge weight. I do both. My powder scale resolves .02 grains and I weigh each charge to +/- .02 grains. To get better uniformity of the case head diameter and extractor grooves I don't mix headstamps or manufacturer batches.
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  #12  
Old 10-18-2011, 05:01 PM
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Re: brass weight sorting

1gr of brass weight variance from such a huge case does imply a waste of time even if it actually correlated to capacity. And, it DOESN'T.
But Run your numbers with 3gr of H20 capacity variance(which is common with larger cases regardless of case weight), and you're lookin at a 50fps contributor to ES.
I don't mean trying to correlate water weight to powder weight, just enter the H20 capacity change with your load in QL.

What's really great is that you can test this easy enough, and find that QL is right.
If you change brass brand or lot and measure the H20 capacity difference, you should then adjust this capacity in QL, and the new velocities it shows will be right.
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  #13  
Old 10-18-2011, 08:02 PM
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Re: brass weight sorting

Quote:
Originally Posted by LouBoyd View Post
I agree with JE Custom in principle. I recently however ran calculations using Quickload to measure the effects of a 1 grain weight difference. The concept is that cartridge brass has a specific gravity of 8.56 compared to water with a specific gravity of 1.0. Therefore a case with 1 grain less brass increases the case capacity by 0.117 grains of H20. .

My calcuation assumed a 300 Win Mag shooting 190 grain Bergers at 1000 yards. I assumed SAAMI seating depth and 75 grains of VV-N560 powder ( a load I use) with a 24" barrel. The increase in case volume (in this example from 93.0 to 93.117 grains reduces the camber pressure and in this calculation dropped the velocity from 2959 to 2957 ftps. The calculated drop at 1000 yards (standard metro and sea level) changed from 311.7 inches to 312.2 inches. A difference of 0.5 inches.

Is a half inch at 1000 yards important? It could be the difference between winning or loosing a 1000 yard benchrest match. It could matter if you're shooting prairie dogs.

I also checked the effect of a 1 grain change in propellant weight. Going from 75 to 76 grains changed the velocity from 2957 fps to 2999 fps, a difference of 40 fps which changes the drop at 1000 yards by 9.5 inches. I think any long range hunter would agree that's significant.

Can brass weight vary without a proportional change in case volume? Yes. When brass is fired the case walls and neck conform to the chamber dimensions, but differences in the case head diameter or the volume of the extractor groove are not reflected in the interior chamber volume. If the weight difference is in the neck it can have other other effect which affect velocity and accuracy.
Neither sorting for weight uniformity or volume uniformity is a guarantee that the walls and necks are symmetrical.

For it to make sense to sort brass to 1 grain it should be obvious that one must also measure charge weights to 0.05 grains or better to make weighing cases have more effect than charge weight. I do both. My powder scale resolves .02 grains and I weigh each charge to +/- .02 grains. To get better uniformity of the case head diameter and extractor grooves I don't mix headstamps or manufacturer batches.
Very good post and a good explanation to some of us that can't express ourselves as well.

First, I agree with the 1 grain batch simply because it is a starting point and gives a good
indication Of the batch quality. and from that 1 grain batch I select brass with the same
exact weight for precision shooting, and if there are enough pieces that are under .5 grains
to load 20 or more I use these for long range hunting also.

I like many also drop powder charges that are as perfict as possible to zero difference.

It does make a difference and if I can lower the Standard deviations by 1 or 2 ft/sec I will take
the time. Is it nessary ? probably not most of the time but confidence is important when
that once in a life time shot comes along.

A rifle is only as good as the ammo and the shooter. so it is worth the trouble to me.

J E CUSTOM
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  #14  
Old 10-18-2011, 08:38 PM
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Join Date: Apr 2009
Location: Elkford B.C. Canada
Posts: 111
Re: brass weight sorting

Quote:
Originally Posted by Boss Hoss View Post
Well if that is your opinion then you are certainly entitled to it. Just because you do not have the means to accurately measure the internal volume that is a process issue that you must resolve. I myself was skeptical of this at first because I wanted an easy way to measure the interior volume of cases. My smith who is a HOF Shooter and has held world records in more than one discipline conducted extensive testing to determine if weighing cases was a valid method for determining volume using Lapua brass for his 6mm PPC and found that it was not.

My testing involved the use of Lapua brass made by Norma (300 win) and it confirmed this conclusion. You are right in that it is a time consuming and tedious process. If it makes you feel better and gives you more confidence at the line then by all means go ahead and do it.

I have asked a friend of mine, A, Mr. Bill Trommer, who holds many records for shooting back in the 70's, about the case weight. It makes a big difference.
If one case weights more than the other, that means that the case is thicker which will cause higher pressure build up in your rifle, which will cause the bullet to fly different from the others.
I should add that quite a few of these records have not been beaten to this day!!
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