AirGunShawn - I bought a CLE (Compass Lake Engineering) 22RF dedicated AR SR upper back in the late '90 to use for practicing offhand & slow prone shooting while I was in the hunt for leg points. It was very accurate, at times out-shooting my Anschutz 1611, and definitely helped me leg-out & earn my Distinguished Rifleman Badge. After I legged-out, I sold that upper to a good friend who was also working on his Badge. Eventually, I missed it to the point that I bought another modified conversion unit & Douglas SS match bbl from CLE, and put together another dedicated 22RF upper. It shoots at least as good as that first one did, and actually out-shot my Stiller 2500XR/Krieger & 40X/Benchmark 22RF repeaters at 200yds with a select lot of SK Std+. My only regret is that I had Frank do the bbl on this one in a heavy SR contour & 20" length, so the resulting rifle is just as heavy as a match grade 223 upper. If I had it to do over again, I'd have had him turn it to a lighter contour, and probably finish at 18" instead of 20", so I wouldn't have to lug around so much weight.
I've never shot anything but match grade std vel ammo through either of those uppers, and at times - especially in cold weather - it'll fail to fully cycle for the first few rounds. I don't know if running hi vel ammo through it would damage anything, but have been shooting it with Lapua Polar Biathlon, which typically chronographs at very nearly 1100fps. That gives better reliability, something that was never a concern when shooting the original upper only in offhand & slow prone. I bought three Black Dog 10rd magazines for it, as I find them easier to load than the little 10rd insert mags that come with the M261 conversion unit. Just wish Black Dog would see fit to reduce the length of these mags to the same as a 20rd GI mag, as they're the same length as a 30rd GI mag, which makes it impossible to shoot off a bench. For bench ammo accuracy testing, I just revert back to the little insert mags. I put a Geissele B-G2S-E trigger in the lower of this rifle, replacing the RRA 2-stage NM trigger I'd set the lower up with, because the RRA trigger gives all sorts of cycling issues due to too much spring tension. The Geissele is a sweet trigger, and improved cycling a bunch.