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Old 12-03-2018, 02:39 PM
foxhunter foxhunter is offline
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just wondering if anyone had done this, load 20 rounds making sure that all powder charges are exactly the same. I use a gempro so I can get it to exact weights. chronograph the loads and sort the cases by standard deviation. then reload and shoot the cases with the lowest standard deviation and see if the group shrinks. might give the same results as sorting cases by weight but would take into consideration other factors that weight alone can't consider, such as primer hole size and it's effect on acuracy.

here is a chart of brass standard deviation by weight. as you can see Winchester and pmc are the most extreme.
Manufacturer
Sample Size
Avg Weight (gr)
Extreme Spread (gr)
Standard Deviation (gr)
Lapua
100
93.35
1.2
0.31
Hornady
50
93.88
1.7
0.43
Lake City ’04
50
92.97
2.5
0.61
WCC 99
50
95.5
2.9
0.74
Federal
50
96.28
2.3
0.75
Remington
50
92.33
4.9
0.85
Winchester
44
93.91
6.5
0.96
PMC
20
93.48
4.6
1.36
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Old 12-03-2018, 02:54 PM
SEM SEM is offline
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Thank you for the time you spent, I wished I had seen this years ago, would of gone to Lapua then instead of just recently. Now that I'm in to tiny groups, instead of just shoot more! their brass doesn't seem so expensive
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Old 12-03-2018, 04:07 PM
flyrod flyrod is offline
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Quote:
Originally Posted by foxhunter View Post
just wondering if anyone had done this...
Yes, and no. For short range I have determined that it doesn't matter. Here is the last time I shot a group at 100 yards:



That is off a bipod in a cheap factory skinny barrel--and it's good enough for what I'm doing. Those are 5 different headstamp cases that vary by at least 20%. Yes, 20% difference in the weight of the empty cases from one headstamp to another.

For long range, I prep and sort brass by weight. Testing showed that 300mg difference in case weight is enough to change mv. At a mile, if a round is 30fps slow or fast it's obvious.
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Old 12-03-2018, 04:41 PM
squirrel_slayer squirrel_slayer is offline
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I have done tons of accuracy testing (case prep, weights, charges, primers, seating depths ect...)

I have found there isn't always a magic recipe. alot of the consistency tricks help no doubt, but I have had some loads that shoot tight at 100yds (in the .3's) but open up further out due to es/sd and vice versus I have had groups shoot 3/4" at 100 with the same gun that is a steel banging SOB on the big end thanks to it's super low ES/SD's

So it really depends on what your doing. for my long range steel banger's I will pick a load with a lower ES/SD over it'y bitty groups. For a varmint rifle I would likely go for the opposite (still need to build my 17)
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Old 12-04-2018, 05:45 AM
georgeld georgeld is offline
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Ol'Bob's sure got a lot of time on his hands!

Guess weighing cases is better than getting drunk
and beating on your wife. (though his wife would win!!)

Wish her well for me.
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Old 12-04-2018, 03:10 PM
Nor Cal Mikie Nor Cal Mikie is offline
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When I was "real active' shooting, my shooting buddy would be busy taking notes while I ran off 200 rounds. Same results. most all going in the same hole.
Once I get my load, I'am pretty much set.
What it comes down to is, "do what you enjoy doing and don't let someone tell you any different". Life is getting WAY TOO SHORT to be making any issues.

George:
If it wasn't for my wife of 54 years, I wouldn't have SQUAT!! Mom always told me "I spent $$ like a drunken sailor".
Don't drink, (cost too much $$) quit smoking maybe 5/6 years ago so now I havn't got any excuses. Just getting old.

Last edited by Nor Cal Mikie; 12-04-2018 at 03:14 PM.
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Old 12-04-2018, 03:22 PM
moorepower moorepower is offline
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Their are probably 3 exceptions to this. The .308, with LC brass, the .30-06 with LC brass and the .22 Hornet. Case volume varies a lot.
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Old 12-04-2018, 05:16 PM
recoillug recoillug is offline
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foxhunter, the question I often wonder about, and don't know the answer to is home much effect the sequence of firing has on MV due to heating of the barrel. Without allowing the barrel to cool all the way down (a very lengthy process with 20 rounds fired) the later rounds would be fired in warmer barrels. So, just how much effect does this have on MV?
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Old 12-04-2018, 06:48 PM
flyrod flyrod is offline
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The way around that is to fire "round robin" when testing. Suppose you have 3 different things you want to test against each other: A, B and C. Instead of firing AAAAABBBBBCCCCC, fire ABCABCABCABCABC. This will also show you how a barrel that heats up affects each of A,B,C.

One case where this sometimes doesn't work well is with completely different powders. Some powders will foul differently, so changing the type of powder with each round may not tell you what you want to know.
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Old 12-04-2018, 07:52 PM
foxhunter foxhunter is offline
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Quote:
Originally Posted by georgeld View Post
Ol'Bob's sure got a lot of time on his hands!

Guess weighing cases is better than getting drunk
and beating on your wife. (though his wife would win!!)

Wish her well for me.
George what we are talking here goes beyond weighing cases and sorting. the next step is to sort by fired standard deviation. taking the sorted cases and make the powder charge exactly the same, fire them and then find all cases with the same or very close standard deviation. reload those cases and fire to see if the group improves,

I don't fight with Alicia, she would put 50 hole thru me. She did that to my friend Randy, he said something she didn't like. she pointed her index fingers at him and made the sound of a machine gun going off. then she blew the smoke away from her fingers and told him "50 holes"
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a well preserved body, but rather to skid in sideways, totally worn out, shouting, Holy sh!t... What a Ride!
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