rim thickness measurements

[15meter]

When rim thickness measuring, do you sort by the thickest rims and use those for accuracy shooting?

What is your criteria for sorting into different groups?

Did you shoot groups to determine the best thickness value to sort for?


What kind of thickness is the minimum that you saw during measurement? Maximum?

[dale2242]

When we were shooting IHMSA 22 RF Silhouettes, I would weigh the loaded 22 cartridge and sort them by weight.
The lightest and heaviest were used for practice.
The ones near the average were sorted into groups of +/- .2 gr.
Those were used for competition.
It did make a difference.

[country gent]

I did sort some for rim thickness. Sorted into batches of .001 thickness shot in groups watching group size and impact shifts between different rim thicknesses.
Group sizes did change some but also as the rims got thicker the groups did shift on the target to aiming point. Up to a "sweet spot" where several thicknesses grouped together.

Sorting by ogive length may be better.

Weighing may help as may checking bullet dia. Also lube may play a part.

[15meter]

When we were shooting IHMSA 22 RF Silhouettes, I would weigh the loaded 22 cartridge and sort them by weight.
The lightest and heaviest were used for practice.
The ones near the average were sorted into groups of +/- .2 gr.
Those were used for competition.
It did make a difference.

Thanks on the weight info, that was going to be the next question, after I got some clarification of thickness measurement.

I'm guessing for rim thickness, you sort for the thickest rim and use those to reduce headspace variation. But that is only a guess.

I know there was a company peddling shims for Ruger 77/22 bolts to tighten them up to reduce headspace variations. They claimed an increase in accuracy with the bolt tighter to the back of the barrel.

Sales hype? Actual improvement? It sounds good in theory, but does it work?

[roysha]

Back in the day, when I was delusional enough to actually think I was a good enough of a shot that measuring rim thickness would make a difference, I bought a Neil Jones rim measure tool. What I mainly discovered with it was the fact that the rims on most of the ammunition I measured were not uniform all the way around. I ended up measuring each cartridge 4 times. (measure, turn quarter turn, measure, repeat) I tried orienting the headstamp the same way each time but the was no good either.
I was able to determine that the group would shift a bit from rim size to rim size. But for all practical purposes, if I stepped up about two level of ammunition quality, and found a lot that my rifle liked, while a bit more costly, I was able to achieve pretty much the same thing.
Just for grins, I checked some Ely Tenex and found even it had a VERY slight variation, both in thickness and circular uniformity. I still have the device and occasionally get it out to impress folks, but in reality, for me and probably a great lot of folks, it is a waste of time. It certainly will NOT make match ammunition from bulk "Walmart special" .22s.

[Mk42gunner]

I have never measured rim thickness, I never got that deep into target .22's. However what roysha wrote makes sense to me.

If I were to do such a thing, I would measure and sort them into a bell curve. Use the outliers as sighters and use the biggest majority for groups, betting on the theory of consistency making better groups.

Robert

[Forrest r]

Bad rabbit hole to go down.

Cheap ammo will never be improved upon with any type of sorting.

You will find (already stated above) that the cheap blammo ammo out there is made for volume not consistence, hence bent rims/uneven rims/as much as 15/1000's difference of the oal at the octive (.223") of the bullet.

Quality ammo tends to have a 38/1000th 39/1000th rim (eley/lapua) and even then, it's their high $$$$ ammo that consistent. Blammo ammo like low $$$ eley/lapua/sk, cci standard velocity, federal 510's, aguila, etc. tend to be thicker. As much as 43/1000th's.

Before you get put on the injured reserve for having a sore thumb, you should measure the depth of the slot in the bolt face of your rifle. Most "common" low grade rifles have +/- 47/1000th's slots in them. Used to redo the bolt faces to 43/1000th's for hunting rifles/blammo ammo and 41/1000th's for target firearms. Then there's the tedious job of resetting the headspace on the bolts and redoing the extractors.

The best thing you can do accuracy wise for your rifle is figure out what chamber you have in it. As you can see different chambers have different lengths from the front of the rim to the leade in the throat.
[IMG][/IMG]

If you're going to do any measuring you should measure the oals of the different ammo you have laying around.
[IMG][/IMG]

Measure and cycle the different ammo's you have. You're looking for an ammo that will engrave the rifling in the bbl 20/1000th's for best results. What happens is the bullet hits the rifling when the bolt closes and is pushed backwards against the bolt face. The bullet gets pushed forward the rest of the getting engraved into the into the rifling as the bolt closes/goes all the way into battery.

The last thing that happens is the quality of your firing pin hit. When you have a fat/wide/long fp hit it tends to disrupt accuracy. It hits on 1 side pushing the rim forward. This not only softens the fp blow/hit, it puts pressure on 1 side of the cases causing it to caulk sideways in the chamber.

What a quality fp shape/hit looks like from a reworked bolt (ruger 10-22)
[IMG][/IMG]

That case has a V headstamp on it. That is the Vostok russian ammo headstamp. It's from the 1980's & is known for it's extremely hard brass that needs sledgehammer its to ignite it. I bought 2 cases of this ammo to shoot in a 25m sport pistol along with using it to test positive fp hits. After reworking that 10-22 bolt the es's got in line with my other tuned rimfires. In line ='s testing with an ammo that consistently ran es's in the 20fps or less. Before reworking the 10-22's bolt I was lucky to keep the es's with that same ammo in the 40fps range.

Why fp hits are important:
Good old ruger, bought a mkIV 45=22 and took it out to see what it could do. Ended up with a pop/pop/bang/click. Tried 4 or 5 different kinds of ammo, no dice. Was getting light fp hits. Called ruger and sent it back, this is what I was getting.
[IMG][/IMG]

Got it back and took it out to see if ruger fixed it. Brought that sport pistol and that russian ammo from the 80's along with a ca bulldog.
[IMG][/IMG]

This is the results of the testing.
[IMG][/IMG]

On the left targets were the 22's. I shot the top 2 targets (5 shots) and adjusted the redots. I moved the russian pistol up (left targets) and did nothing to the ruger's redot (right targets). Shot another string on the lower 2 targets. The russian pistol with it's excellent fp hits held all 5 shots in the 1" white center @ 50ft with that +/- 40 year old ammo. The ruger kept having fliers with a new box od ww ammo.

The fliers are from weak fp hits. I ended up reworking that 45-22's bolt and the fliers went away.

Anyway all the measuring in the work won't help if the firearm isn't mechanically sound/consistent. Then the differences in the quality/dimensions on the ammo you're using come into play.

[Rapier]

Yes, I measure all of my ammo, every componet in center fire. On 22 RF ammo weight, length and rim thickness. Have a dial rim gauge and uniforming dies. Bought ammo of the same lot by the thousands and sorted out the exact same weight, length and rim thickness. If you shoot in the highest rated class in competition, where you only shoot in your class, you actually only go to a one shot match, miss one shot and you loose.

For production, revolver and standing, used Federal Classic, prepped and in Unlimited used the Federal Olympic Gold Ultra Match standard velocity to keep the change from super to subsonic from being at 75 and 100 yards.

[Forrest r]

The dimpled Federal Olympic Gold was good back in the 90's. Every time I see that ammo being used now (modern/newly made) it's at the club level and mostly 50ft indoor pistol/revolvers. It's defiantly a step above the cci sv, auto match, and other low $$$ offering shooters use.

Federal has it for $80 a brick.
https://www.bing.com/ck/a?!&&p=9e50a...Qi5odG1s&ntb=1

The only thing I've ever seen or used that aided in a more consistent/accurate mid-grade rimfire ammo. Is anything the made the bullets a more consistent diameter. Tools like the d-rock tool, waltz die and the paco kelly tool are used to "accurize" ammo. I never used the d-rock tool, but it always had excellent reviews on rim fire central. Was on that website when he 1st started making/selling them. He's one heck of a great guy and did volumes to not only support rimfire shooters. He helps them excel at the sport.

I have and still use the waltz die and the paco kelly tool from time to time. But as with anything when dealing with low quality/blammo ammo. Some times it helps, other times it makes it worse.

Step up to mid-grade match ammo like the federal gold mentioned above or the sk offerings and those tools start to show their value.

[15meter]

Still listening, not sure which way to go on this. Tried the weight sort bit on two boxes of Wolf match extra. I believe It helped. Did not shoot enough to get any definitive answer. Group tighten up enough I won a simple local match yesterday. Biggest problem is not enough magnification for the target we used. 10 rounds into 1-1/2" at a hundred yards is still respectable for a sporter weight rifle. In a 6-8 mile an hour wind.

This is more my seeing how much I can wring out of a sporter weight rifle and tweak the pots of several deadly serious rimfire shooters.

Kind of like me shooting a Sheridan Silver Streak or a Benjamin 317 in the club air rifle matches against Feinwerkbau's and Anshutz's.

I won enough, it had a couple of them talking to themselves.

Need to finish the rim thickness gage when it cools down a little bit. Approaching 100 degrees in the shop today.

Then make a bullet swaging tool.

The life of an old guy, it's hard work, but somebody's gotta do it.