I've written before about the cost of ammunition for high power rifle competition, coming in at $0.25-0.30 a round. Match grade smallbore (.22LR rim fire) ammunition, by comparison, can be had for $0.08-$0.10. "Practice grade" smallbore ammunition can be had for $0.03-$0.05. Shooters of various disciplines seek out rim fire ammunition to practice with because it's cheaper, quieter, and has less recoil. In the case of high power rifle practice, savings are amplified by the saved barrel life on a match rifle, which may only have a "match grade" life of a few thousand shots. In contrast, a smallbore barrel lasts practically forever--hundreds of thousands of rounds.
For those unfamiliar with the AR-15 rifle platform, it consists of two main sections: 1) an "upper" which consists of the barrel, bolt carrier, and upper receiver, and 2) the "lower" consisting of the serialized receiver, trigger group, and butt stock. The upper can be removed and replaced with one of a different configuration, or even a different caliber. So one option with the AR-15 is to have a dedicated .22LR upper. Another less expensive option is a .22LR conversion kit, which uses the existing upper and barrel. Conversion kits are fun, and perfect for some disciplines. But their accuracy is nowhere near as good as dedicated .22LR upper with a match chamber and a twist rate (1/16) intended for .22LR as opposed to .223 (1/7).
I've had a .22LR Service Rifle upper for my AR-15 from Compass Lake Engineering for roughly a year. In the past I used it to practice rapid fire sitting and prone stages with a "practice grade" rimfire ammunition, Eley Sport. It would produce good groups, but random fliers would appear, which I would just ignore. But having recently started with NRA Smallbore Prone matches, I began to wonder what kind of results I could get shooting prone with the same ammo I use in my bolt action Anschutz smallbore rifle, Wolf Match Target. So I decided to use the recent Labor Day holiday to give it a go.
All of my testing was performed from the prone position with a sling. The results were outstanding, yielding great 50 yard groups as shown above. I only had time for one 100 yard go, but again the results were outstanding. The target below is somewhere between 15 and 20 shots in a medium right-to-left wind. The lone 8 was caused by me figuring out the windage adjustments are not as fine as the Anschutz sights, but once I got it dialed in I was able to hammer out 10s. With better wind calls I'm sure the 9s will merge into 10s.
I'm so pleased with the results, I'm going to use the CLE .22LR upper with my AR-15 instead of my Anschutz at this weekend's smallbore prone match! In theory, it should be harder to shoot well for several reasons. For one, the shorter sight radius, which is the distance between the front and rear sight. In theory, the longer the sight radius the more precisely one can aim. Also the CLE has coarser sight adjustment clicks than the Anschutz, as I believe my Anschutz has the older 1/6 minute clicks whereas I know the CLE has 1/4 minute clicks (which seemed to match my need to use roughly 20 clicks on the CLE to come up from 50 to 100 yards, versus 38 clicks up on the Anschutz sights). My AR lower has a 5lb. trigger, although it's a 2-stage trigger with about a 1lb. second stage let off, wheras the Anschutz second stage is probably about half that. Lastly, the CLE uses a Service Rifle front post sight, compared to the Anschutz being outfitted with adjustable iris apertures.
But all that theory aside, because I spend so much time practicing with the AR-15 as opposed to my smallbore rifle, everything feels more comfortable and familiar.