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Old March 5, 2000, 02:27 PM   #1
DOCSpanky
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Join Date: August 21, 1999
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I am looking for a rimfire rim thickness guage. Bald Eagle makes a fine one, but I just dont have $89.00 to lay out now. Any other suggestions?

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Old March 5, 2000, 02:36 PM   #2
Mal H
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DOCSpanky, why do you want one? This is a serious question. I have heard some say that separating by rim thickness will help improve groupings. But no one has any real proof that this is true. I follow the discussions on the benchrest forum and everytime the subject comes up it is shot down. Several very serious benchrest rimfire competitors have tried it and said it made no difference.

The biggest difference you can experience is by using a premium line of ammo, and there are a lot of them. Those makes will have already done the rim thickness job for you anyway.

Benchrest rimfire forum: http://benchrest.com/rimfire_board/
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Old March 6, 2000, 02:16 AM   #3
bk40
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Neil Jones Custom Products makes a less expensive gage - check with Sinclair or Neil. I've found rim thickness variations in all of the premimum rimfire ammo. Segregating ammo has helped me.
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Old March 6, 2000, 12:19 PM   #4
Mal H
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bk40 - can you quantify how much sorting by rim thickness has helped? Again, I'm serious because if it will give you .1" smaller groups, for example, compared to non-sorted then I'm going to get one also. But, I have never found anyone who says how much it really helps. I often think it may be that you really want it to work and so it does. You might be taking a little more time aiming, just to be sure.
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Old March 7, 2000, 04:21 PM   #5
bk40
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Mal,

I've been able to reduce group size at 50yds (segregating by thickness) by as much as 0.15". In BR rifles and pistols the reduction is usually smaller than in production guns such as a fine Kimber of Oregon rifle.

The best use I've found for rimfire thickness gages is the ability to take standard velocity ammo from Winchester, Remington... and obtain match ammo like accuracy with the cheaper stuff. Groups with std rimfire ammo can be reduced by as much as 0.3" at 50yds using this method.

With top quality match ammo, (Eley, Federal Match, Lapua...) lot to lot variations will normally have the greatest effect on accuracy, I've found. To eek out the tiniest bit of accuracy its usually necessary to segregate by rim thickness and weight, but we're talking less than 0.1" difference in match chambers with match ammo 50yds.
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Old March 7, 2000, 06:50 PM   #6
Mal H
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Thanks. That is a significant reduction in group sizes, even if only .1".

I'm still not completely convinced due to the multitude of benchresters that poo poo it. I would like to borrow a gauge from someone around here and do a blind grouping test to see what happens.
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Old March 8, 2000, 11:11 AM   #7
slickpuppy
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The biggest advantage I found when using a rim thickness gauge is that I am able to cull extremely thick and thin rims from the lots. That, in conjunction with a weight sort has eliminated the mysterious flyer problem for me. What I found in my testing with several .22 rimfire pistols(S&W 41, Colt Trooper, Ruger MkII) fired from a Ransom Rest at 50 ft., with 25 varieties of .22 rimfire ammo, and sorting by OAL, rim thickness, and weight is that the extremely thin and thick rims cause the flyers. My guess is that this is due to the nonuniform distribution of the primer compound in said cases. Some of the cheaper .22 varieties will group much tighter with the above sorts. How much better? Depends on the variety and the gun it is shot from. I have a stack of targets for each gun and its performance with each ammo variant. Yes, this stack is over 6 inches high. As for where to get one, Champion's Choice and Sinclair International both sell them as well as Neil J. As for what I shoot now, I found that CCI's products are the best value and most consistent for the money. I can shoot a lot more CCI Blazer than Eley Tenex!

[This message has been edited by slickpuppy (edited March 08, 2000).]
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