Rimfire Rim Thickness Gauge?

O

oxnam

New member
I shot in an indoor league for a few months and we always sorted our 22 LR ammo by the thickness of their rims. I don't remember who made the gauge, but it was very simple to use. All you had to do was slide the rim of the shell into a slot and the thinner the rim, the deeper it would go. There were corresponding numbers 1, 2, 3...along the slot and they were sorted according to the number that they lined up with. Has anyone ever used a gauge similar to this or something else that accomplished the same thing? I noticed Stoney Point makes one but it looks slow and you have to use calipers with it. Any suggestions would be appreciated. I figure it would be great for my 22lr as well as my 17 HMR.
thanks,
oxnam
 
This has been done for 25 years or more.
Sometimes it seems to help a bit but othertimes not.
It is probably mostly a psychological thing having no real physical benefit.

The US Olympic smallbore team tried it for a while but gave it up.

Jack
 
I wonder if they gave it up because of the quality of ammunition they were using. I would imagine the more expensive stuff would be more uniform. What got me thinking about is was the groups that I shot with my T/C Contender 10" and 14" last weekend. One five shot group at 50 yards had three shots in a tight little clover and then one half inch left and the other a little high and right. I switched barrels and shot 10 rounds. Five were in a tight little group and the rest were hitting different places. I am shooting the cheap Remington stuff and thought that it might help with the fliers. Just a guess though.
 
I have done some testing of rimfire ammo sorted by weight and rim thickness. I sorted ammo to .1 grains by weight and .001 in rim thickness. I did this for 5000 rounds of Wolf Match target, and hundres of rounds of other ammo, some cheap bulk ammo and other inexpensive box ammo. I also sorted several hundered rounds of the other higher end ammo, like RWS 50 and 100, as well as SK's match ammo.
In summary, the cheap ammo, bulk, or boxed, can not be made to shoot better by sorting. It's just cheap ammo that will never shoot benchest accuracy. The Wolf Match Target did see significant improvement in accuracy by weight sorting, but sorting by rim thickness produced no improvement with this ammo. And, sorting by rim thickness showed no improvement in any other ammo either. The very expensive target ammo, like Lapua and Eley, does not need any sorting as it's dead on in both areas when it comes from the factory.
So, I've taken Wolf Match Target that costs $3 a box and made it shoot as well as ammo costing $12 per box. I did no comparing of the other ammo, like RWS 100, that I did sort and shoot, but only shot it sorted, and have no comparison to how it shot without sorting. By the way, that RWS 100 sorted shoots extremely well, just like Wolf Match Target sorted. It depends on what rifle shoots each ammo best.
I have about 20 high grade 22 Rifles, and most shoot the Wolf best of all ammo tested. I have much of the high end ammo that I test, along with Wolf, with each rifle to see what ammo it likes best, and Wolf does well in most.
When I sorted Wolf, and shot it in a Suhl 150 (very accurate rifle that shoots Wolf best), I found that a difference in ammo weight of 1.2 grains produced groups that were separated by 1/2" at 50 yards for 5 shot groups. No difference in poi could be determined by shooting ammo with the widest variance in rim thicknesses; it all shot in the same hole.
So, I've given up on sorting by rim thickness, and do sort only Wolf by weight. All of the testing was in support on my 22 Rimfire benchrest shooting. If a particular rifle I'm shoot likes the $12 a box lapua ammo best, I do no sorting of it before shooting a match.

Martyn
 
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Quote:
This has been done for 25 years or more.
Sometimes it seems to help a bit but othertimes not.
It is probably mostly a psychological thing having no real physical benefit.

The US Olympic smallbore team tried it for a while but gave it up.

Jack



I made up a tool to measure the rim thickness on .22 Mag shells. I was shooting Winchester 34 grain premium shells at the time since they had the best terminal performance, but I had noticed vertical stringing of groups at 100 yards, with the shells bolting down hard, tending to shoot high. The groups tended to be about 1 1/2" to 2" high by about 3/4" to 1" wide. The consistent vertical shot stringing was noticible and when chronographing some shells, I had extreme spreads of over 100 fps.

I had a Marlin 882, heavy barrel, that I had glass and pillar bedded, so I was fairly confident that bedding was not the reason for the problem.

There was a wide variation in rim thickness on those shells, over .006", if I remember correctly. And, sorting by rim did significantly improve groups in my gun. The thick rimmed shells grouped well, but shot as much as an inch higher at 100 yards from the middle group, which also shot well. The thin rimmed shells, didn't group well and I just used them for fouling the barrel.

In measuring rims on CCI shells, I found very little difference in rim thickness. I never used CCI .22 Mag shells since they didn't perform as well terminally in friend's guns as did the 34 grain Win. HP's, though
 
I used to do that when i shot small bore competition in high school (way more than 25 years ago)It has to do with the headspace and keeping the ammo seperate for each individual rifle. I do not rememeber how many thousanths of inch we would go after but the rifle I shot all the time was a three on the gauge we each gauged and selected outr own ammo, for practice and before a match. The rifles belonged to the school, (that should give you an idea how long ago it was. Acctually I could by Govt surplus rifles by mail then and they would be shipped right to my front door. ( see what I mean times have really changed I guess.
 
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