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procedure for measuring case volume

 
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  #43  
Old 04-07-2012, 10:44 AM
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Re: procedure for measuring case volume

great thread.
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  #44  
Old 04-07-2012, 04:38 PM
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Re: procedure for measuring case volume

Good method & good brass Richard.
Did you happen to record empty case weights? Not that it affects YOUR outcome, but curious as to what others might have culled.
How do you normally size for use in a match?
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  #45  
Old 04-09-2012, 09:55 AM
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Re: procedure for measuring case volume

Quote:
Originally Posted by Mikecr View Post
Good method & good brass Richard.
Did you happen to record empty case weights? Not that it affects YOUR outcome, but curious as to what others might have culled.
How do you normally size for use in a match?
Mikecr,

I've never been in or to a match. I have my son signed up for his first 500yd clay shoot in 2 weeks. He's a good shot and I think we built a nice rifle. But, I have no idea what to expect. We are learning as we go and appreciate all the help we get here.

No brass was culled as yet. These were 50 random cases from the first box of 100 that were used for load development and this was the 4th firing. I have another 250 pieces that have been fire formed and ready for prep/sort/culling.

Brass prep was as follows:
- load and shoot with no prep
- partial neck size with Redding Type-S just more than bullet bearing surface and (.002" below cal)
- trim to 1.555" using Wilson trimmer
- inside neck chamfer with K&M
- outside neck chamfer
- steel wool case mouth with hand drill
- flash hole and primer pocket uniform with K&M
- seat CCI BR4 primers with forster co-ax
- 30.20 grains Varget
- sort and group bullet ogive to boat tail by .010" buckets
- weight sort and group bullet buckets by .04 grains
- seat bullets with Wilson micrometer seater

Wind was light but variable. Sometimes R2L and sometimes L2R. Technique was to wait for wind flags to be consistent. If wait seemed too long, then he held off to compensate. All groups were sub-MOA @ 500yds. Most were under 2".

Most of the groups were just shooting for group size to evaluate the rifle/ammo. But, he did go ahead and dial mid way through to achieve POA/POI. That is going to be a huge challenge if he can't spot his own shots as this match doesn't allow spotters.

See table below including empty case Wt.
Note: MV in 4th column and MV stats per string to the right.
I left the chrony in the other car and didn't get MV for the last 20 in the afternoon.

Code:
CaseWt	Case+H2O-Wt	H2O Wt		MV	Mean-MV	Stdev-MV	ES-MV
127.34	165.56	38.22		2687			
126.80	165.14	38.34		2734	2710.5	33.2	47.0
126.92	165.34	38.42		2738			
125.52	164.10	38.58		2734			
126.60	165.20	38.60		2726	2732.7	6.11	12
126.94	165.54	38.60		2730			
127.22	165.82	38.60		2726			
126.94	165.56	38.62		2722			
127.24	165.86	38.62		2726			
126.84	165.50	38.66		2727	2726.2	2.86	8
126.50	165.18	38.68		2764			
125.98	164.70	38.72		2766			
126.82	165.54	38.72		2764			
126.38	165.12	38.74		2765			
127.12	165.86	38.74		2744	2760.6	9.32	22
125.90	164.66	38.76		2760			
127.04	165.82	38.78		2763			
127.34	166.12	38.78		2761			
126.22	165.04	38.82		2764			
127.52	166.34	38.82		2758	2761.2	2.39	6
126.08	164.92	38.84		2759			
126.96	165.86	38.90		2754			
127.06	165.98	38.92		2765			
127.48	166.42	38.94		2761			
126.68	165.62	38.94		2763	2760.4	4.22	11
126.86	165.82	38.96		2768			
125.88	164.84	38.96		2777			
126.60	165.56	38.96		2771			
126.88	165.84	38.96		2768			
126.06	165.04	38.98		2784	2773.6	6.88	16
126.40	165.38	38.98					
126.26	165.24	38.98					
127.04	166.04	39.00					
126.96	166.00	39.04					
126.56	165.62	39.06					
126.26	165.34	39.08					
126.86	165.94	39.08					
126.88	165.98	39.10					
126.86	165.96	39.10					
126.86	165.98	39.12					
126.34	165.48	39.14					
125.24	164.38	39.14					
125.98	165.12	39.14					
126.70	165.86	39.16					
125.96	165.14	39.18					
126.74	165.92	39.18					
125.72	164.92	39.20					
126.60	165.82	39.22					
125.90	165.16	39.26					
125.98	165.26	39.28					
126.60	165.49	38.89	mean				
0.53	0.49	0.25	s				
125.24	164.10	38.22	min				
127.52	166.42	39.28	max				
2.28	2.32	1.06	range
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  #46  
Old 04-11-2012, 09:05 PM
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Re: procedure for measuring case volume

Richard

After doing this, what do you think it showed you about case weighing vs capacity when you look at the extremes of weight, capacity and the resulting MV variances or non variances expected?

As I said earlier, I cannot get it to show me any positive result on reducing ES overall. Cases that show wide gaps in range shoot closer and cases that are close show wide MV gaps that should not be there IF case capacity was really accurate as an indicator.

I have used an Oehler 35 with both 4 ft and 8 foot spacing, so I am confident my MV is as accurately measured than 98% of anything else other than commerical models.
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  #47  
Old 04-12-2012, 06:39 AM
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Re: procedure for measuring case volume

Quote:
Originally Posted by rscott5028 View Post
See table below including empty case Wt.
Note: MV in 4th column and MV stats per string to the right.
How much of the velocity spread was caused by the primers?

How much of it was caused by inconsistant rifle holding?

And how much was caused by the normal velocity spread of exact weight powder charges?
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  #48  
Old 04-12-2012, 10:47 AM
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Re: procedure for measuring case volume

Quote:
Originally Posted by BountyHunter View Post
Richard

After doing this, what do you think it showed you about case weighing vs capacity when you look at the extremes of weight, capacity and the resulting MV variances or non variances expected?

As I said earlier, I cannot get it to show me any positive result on reducing ES overall. Cases that show wide gaps in range shoot closer and cases that are close show wide MV gaps that should not be there IF case capacity was really accurate as an indicator.

I have used an Oehler 35 with both 4 ft and 8 foot spacing, so I am confident my MV is as accurately measured than 98% of anything else other than commerical models.
I don't want to be too quick to draw conclusions from one small sample set. But, here are some thoughts...

From the data, I do not see a direct correlation between case weight and case capacity with this lot of brass.

I think it shows that Lapua brass is pretty consistent to begin with. ..only 1gr spread although 6br is a small cartridge to begin with. Perhaps testing with a WSM or RUM would yeild different results? Or, possibly I'm at or near my "node" where small variance in the load isn't going to have as much influence on performance?

With the brass all sorted in ascending order by water weight capacity, it appears that velocity goes up as case capacity increases while holding powder charge constant.

However, that's reverse from my prior understanding. (Perhaps someone might explain?) ...although the shots were fired throughout the morning as the temperature warmed. So, it's likeley that ambient case temperature has more bearing on MV than minor containment variation.

I think the ES/SD for the samples was pretty good. And while I might attribute that laregly to good brass and careful case prep, I think I'll continue along this path for at least another batch or two before I deviate from something that appears to be working. ...even if I don't know for sure exactly why it's working.

-- richard
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  #49  
Old 04-12-2012, 11:06 AM
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Re: procedure for measuring case volume

Quote:
Originally Posted by Bart B View Post
How much of the velocity spread was caused by the primers?
I don't know. I use benchrest primers because I expect them to be more consistent. It would take a much more sophisticated study to isolate that as a variable.

Assuming individual primers within a lot have much variability, I wouldn't know how to sort them prior to shooting and once the hammer drops, it's too late to recall the bullet.

Quote:
Originally Posted by Bart B View Post
How much of it was caused by inconsistant rifle holding?
I think the rifle was positioned and held as well and consistent as can be expected without a machine rest. I think the low ES/SD might support that. But, that's not to say that there might be shot to shot variability introduced by the shooter's hold. e.g. There were a few with high MV that could be the result of a firm shoulder or possibly letting the cartridge warm too long waiting for the wind. Similarly, there were a few with low MV that might be from a loose grip/shoulder.

I assume that's what your question relates too?

Quote:
Originally Posted by Bart B View Post
And how much was caused by the normal velocity spread of exact weight powder charges?
The powder charges were carefully weighed to the nearest .02 gr which is tighter control than the typical reloading scale is capable of. I re-verified the empty tare weight of the pan frequently and didn't observe any drift.

So, I think I did the best I could to manage that variable.

I will say from the group size and POA/POI that practice and reading conditions from shot to shot and string to string is many times over more directly correlated to actual results.

e.g. His best group was about 1.5" with only about .2" vertical spread which I'd be tickled with any day. However, it was about 2.5" low and left which would've been either a near miss or a goose egg on the largest 3 of 8 clays in the upcoming cometition.

Hence, my son needn't consternate over the minutia of case volume and primers. He needs to focus on technique, flags, and mirage. Since I'm not the trigger man, I have no problem toiling with it for a while.

Thanks for the feedback!
-- richard
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