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Discussion Starter · #1 ·
Hi all,

I'm usually on the Big Bore forum, but decided to go small today. Hope you guys don't mind me posting or maybe asking a question that has been beat to death prior.

I recently made up a gauge, with a dial indicator, for measuring rim thickness on 22lr rounds. I've heard about it for years, but never tried it. I segregated a bunch of rounds from a brick of Walmart special Federal Lightning HP's. I found that the rim thickness was from 0.060 to 0.064 inches. I separated them into lots of 10 rnds each plus 10 rnd of random picks. I fired them from a bench at 50 yard with my Anschutz Model 54 1700. Here's what I ended up with;

Mixed lot: 1.50" for 10 rnds
0.0635 lot: 0.88" for 10 rnds
0.0630 lot: 0.63" for 10 rnds
0.0620 lot: 0.38" for 10 rnds

I was shocked at the results. Not only by just sorting for a common rim thickness, but to find the perfect thickness for the headspace. I also checked out a bunch of RWS match ammo for grins. Their variance was about +/- 0.0005" from the 20 rnds I had left. Has anybody on this forum done this before?
 

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Hey BABore -
I have never sorted by rim thickness, but I have heard it makes a great difference in group sizes. However, I have thought about it a bit. What I came up with was an idea of how to reconfigure the rim thickness so that they are all fairly consistent. I toyed with the idea combining a swaging die with a rim guage, and attempting to slowly swage the rims to a uniform thickness......considering that a rimfire by nature has a "sensitive" rim, mashing the rims kinda struck me, as, well, stupid. In theory it should work, but I don't think I could admit to trying it :roll:

Shum8
 
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Discussion Starter · #4 ·
With the gauge that I made up I can measure 8-10 rnds a minute. Next time I get the camera out I'll try to post a picture or put it in my photo gallery.
 

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BABore-

I tried measuring rims with a similar set up involving a dial gauge, and had quite similar results. Lapua Biathlon competition ammo showed the least variance- tolerances were so close that I gave up on trying to measure them after 100 rounds.

I think that rim thickness variation is the major thing to look for in rimfire ammo. Sorting by weight does little to tighten groups, I've found...

Regards,

Doc Sharptail
 
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