Quoted:
For stability in flight, the heavier the better with your twist. Don't expect much.
That said, Fed bulk pack kicks ass and take names.
First post as usual. The fast twist of an AR (1:7, 1:9, etc.) are actually
too fast and tend to
over-stabilize the slower .22LR rounds, so heavier is indeed better. Accuracy will still not approach what a dedicated 22LR upper will provide, but is sufficient for practice drills and even small game hunting if the ranges are kept short. I love my CMMG unit though and the Federal bulk pack ammo has been pretty much a 100% performer. CCI is also great stuff in my experience. But by all means
stay far, far away from Remington "Golden Bullet" bulk packs! I've had more misfires and squibs with that ammo than anything you'd believe short of wasting the money and seeing for yourself. It's not just confined to the CMMG unit either. That junk doesn't work in my 10/22 either.
ETA- FWIW, my conversion is parkerized, not stainless, and has not given me any issues. When I first got it, it was a really tight fit into the chamber but it wore-in very quickly.