After testing weight sorted cartridges of Federal Champion 22LR LRN and finding that they produced 60% smaller groups than non weight-sorted cartridges, I decided to test the other big old-school 22LR accuracy technique: sorting cartridges by rim thickness.
The thickness of the a 22LR rim can effect the amount of headspace of the bullet in the chamber. And presumably, the thickness could also effect the amount and burn rate of the primer inside it. Both of these factors could effect the velocity and stability of a .22 bullet.
For the test used a batch of weight sorted 22LR cartridges from which to draw my rim sorted samples from. All the cartridges I measured weighed between 51.3gr and 51.5gr. I put 50 aside as a control group and measured the rim thickness of the remaining cartridges and sorted them by rim thickness. A friend from my rifle club lent me his Neil Jones Rimfire Gauge tool which made the measurement process relatively quick.
For my testbed I used my same CZ 457 VPC that I used for the weight sort test. At the range, I set up 2 rows of 3″ paste up targets at 100yrds. I fired 5 rounds into each target for a total of 40 rounds of rim sorted and 40 rounds of my non-sorted ammo.
Upon inspection the target groups were each a bit different from each other but overall appeared relatively similar in size. Just how similar surprised me after I ran a photo through my phone’s Range Buddy App. On overage both the rim sorted and the randomized control group produced a 1.27 MOA average size. Identical.
1.03 1.28 1.61 1.16 MOA
Avg 1.27 MOA
1.83 0.99 1.14 1.14 MOA
Avg 1.27 MOA
So it would appear that rim thickness plays an insignificant role in 22LR accuracy and performance. At least so far as Federal Champion LRN is concerned. My buddy who lent me his Rim Gauge told me as much when he tested his Match Grade 22LR for competitions. Were it not the case, I doubt he’d be lending me his gauge.