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.

RIM SORTED
1.03 1.28 1.61 1.16 MOA
Avg 1.27 MOA

RANDOM CONTROL
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.

While competing at a 100yrd match with my new CZ457 with a 6-24×50 Vortex Diamondback Tactical I noticed a flash of something when firing at the bullseye. At first I didn’t know what it was but after seeing it again the next time I fired, I couldn’t believe that I was seeing the bullet in flight to the target.

I know you can see the shockwave mirage of a bullet in flight at long range (over 500m). But in 40 years of shooting I’ve never heard nor seen a bullet at 100yrds. Much less a tiny bullet like a .22cal.

After the match, I set up up my camera on the scope and tried to capture what I was seeing. It requires the right lighting conditions (the sun was directly at my back) and a high-quality magnified scope with ED glass, but this footage shows that it is possible.

I competed in my 2nd match with my new CZ457 VPC. A made a few minor changes to the setup. I returned my Athlon Argos to my AR and replaced it with a Vortex Diamondback Tactical 6-24×50; the finer reticle lines makes spotting .22cal holes easier. I lightened the factory-stock 3lb trigger pull to just under 2lbs.

Perhaps the biggest change in performance came from the ammo. Instead of running CCI Standard again, I stumbled upon the performance potential of Federal Champion when I used it to initially sight in the Vortex Diamondback (not wanting to waste my limited match-grade ammo). I noticed the surprisingly small group it was printing. I ran out of time before the match to properly test other ammo, so opted to take a risk. I ran with “Blue Box”.

I ended up winning the match, coming in 1st place to my utter surprise. It was a very close score. I scored only two points more than the next highest scoring competitors. I hope to fine tune my setup and find an even better ammo than “Blue Box” for the next match. But if it turns out this is the best ammo for this rifle, so much the better as far as my wallet is concerned.

Stay tuned for more ammo test videos.