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velocity based case sorting

 
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  #1  
Old 09-19-2004, 06:03 PM
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velocity based case sorting

Well, I've got a new itch to scratch, so to speak.

I recently had a long conversation w/ a gentleman that is a serious F-Class and 1K BR shooter. The topic of sorting cases came up, water volume vs. weight sorting, weight sorting into 1-2% big batch vs. making up 0.5gr lots, etc. He had a different approach that on the surface seems to makes sense (sure seems to be working for him!), and I though I'd run it by y'all and see what you think about it.

He gets a (very) large quantity of cases up front, (Lapua .30-06, in this case, as his round is a 6.5-06), and completely preps them, i.e. primer-pocket uniforming, flash hole deburring, trim, chamfer, deburr, neck turn, the whole enchilada. Then he loads them up w/ a known good load that shoots fairly consistently, stable velocity. *All* of them. Fires the rounds one at a time, one every three minutes to keep the barrel temp stable, chronographs every one, and writes the speed on the case itself w/ a sharpie. Loads them up again, and does this again.

At this point, he has all of his cases fired twice, as fully fire-formed as they are going to get (btw, he uses a separate barrel chambered up w/ the same reamer so one barrel is for fire-forming and load workup, the other is his primary 'match' barrel), w/ velocities written down on them. He then sorts them by what his target velocity, E.S., and S.D. are. I.e., if he wants an average velocity of 2950fps, w/ an extreme spread of 10fps, he'd gather all the rounds that went that speed into one 'lot', and keep them together for the rest of their natural life (15 loadings total). He feels this is the most realistic way to sort cases, as you are not dealing w/ variables of case head dimensions affecting weight/volume, surface tension/bubble affecting water volume, etc. Just measuring what the actual real world speed is out of these cases.

Sounds good. Expensive and time consuming, but if you are really after the lowest E.S. and S.D., it might be worth it. Not sure how the variance within even an individual powder or primer lot, or the finite accuracy of the powder scale or chronograph would play into this. As I said, the guy is shooting pretty competitively, and firmly believes having effectively zero E.S. is a big contributor.

Comments, thoughts, suggestions?

Thanks,

Monte
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  #2  
Old 09-19-2004, 10:54 PM
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Re: velocity based case sorting

Interesting. I've never heard of this, but it makes sense. Rather than trying to measure all the little things that create variation, just measure the variation itself and don't try to figure it out - just live with it. I think I like it (at least, it's worth a try).
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  #3  
Old 09-20-2004, 04:36 AM
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Re: velocity based case sorting

John Hoover in PA does that for the 6.5-284s his family uses. Based on results it sure works. They shoot light guns in the heavy gun class and kick but normally.

By the way he only uses "old white box" WW 284 brass and has a couple unique steps in his reloading process.

I use a Juenke machine to do something similar. After fireformed, the cases are spun on a Juenke and sorted by deviation units and that seems to work also.

BH
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Old 09-20-2004, 07:13 AM
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Re: velocity based case sorting

Milanuk, I think your friend has the right approch. I don't load for the long range game but have heard the es if more than 10 can account for different size groups at 1000yds. I think some case prep is ok but you still have to fire that round and be able to slect those match case and alot of different methods to doing that.
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Old 09-20-2004, 12:08 PM
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Re: velocity based case sorting

Monte, I do something very similar and it has really helped me with consistent groups. Instead of just measuring vel, I shoot for group size.

The min. distance I shoot at is 180yds (just the way my range is). 250yds is better. Assuming conditions are calm, I shoot groups with the best shooting load. I look for any shot 'out of the group'. I mark the brass. Odds are, that brass fired again will throw the shot out. I pitch that brass.

What I have left over is brass that is consistent UNDER FIRE. They may vary when you measure different aspects but that doesn't bother me.

I have tried the weight and volume method. Both can give bad results for various reasons. The only way to know about the brass is to shoot it. By doing this, I have been able to get match quality from gunshow mystery stuff to mixed lot onced fired.

I find that annealing the necks can help increase consistency when dealing with mixed lot mystery stuff.

It is expensive and adds wear to the rifle but I need the practise anyways. It will give you the best brass I know how to 'make'.

Jerry
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  #6  
Old 09-20-2004, 01:45 PM
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Re: velocity based case sorting

Jerry,

I told the fellow I'd heard a similar method, basicaly keeping the shells that shot an 'X' (from an old score BR shooter) in one coveted pile. His response was that he felt the chrono method eliminated any human error factors. Still, it's interesting to see that others employ similar methods.

The big thing that was daunting about his version (other than the extra barrel) was the *2000* pieces of Lapua brass he starts with. That's over $850 in brass _alone_!!! Yikes. But, as was mentioned, if winning is the goal... it apparently seems to help.

I was kind of hoping to employ a variation w/ a couple of upcoming .308 Winchester projects. 500 pieces of brass dedicated to each gun, and velocity sort them into 'batches'. I didn't figure 500rds of test firing was too much of a chunk out of the respective lives of a .308, and probably would provide some much needed trigger time. Afterwards I hoped to sort the brass into say, 50rd batches, and keep them separated in the blue Dillon shell boxes. For the one rifle (long range prone - any-any/F-class/Palma), most all the shooting is for 'score' so keeping the shots consistent in velocity/elevation in one box would work just fine. Minor changes from one box to the next would be relatively easy to account for. For the other gun, which is more for hunting and/or tactical matches, going from one box to the next could be an issue. I don't really hunt LR all that much w/ a .308, so that part wouldn't be too big a deal, but for the matches having to know where the cold bore shot was going to go could be interesting, depending on which 'box' I'm using.

Ah, well, it'll give me something else to worry about [img]images/icons/wink.gif[/img]

Thanks,

Monte
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  #7  
Old 09-20-2004, 02:04 PM
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Re: velocity based case sorting

Somebody try it.
Take one formed case/load, measure it's resultant velocity over a chrono.
Then reload same and measure again.
Maybe try it a third time.
Does it work?
Let us know.
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