On another project we ended up trying two .22 conversions in an AR pistol, one from the 60s and a modern CMMG unit. Both worked in the test rig, and I went ahead and ordered a CMMG unit for myself. Picked it up from Primary Arms, they had a good deal and shipped it quick. No super break in or high round count, just popped it in my 'good' AR, tossed the rimfire can on and it ran perfectly well with CCI standard velocity ammo (of which I have a ton of). I'm curious to know if any of you have high round counts through one using lead ammo instead of the recommended copper bullets?