Chris
Nice going!
As far as .22s go, just get a Ciener or other brand .22 kit and shoot it in your current upper. It won't hurt a thing, and it will surprise you how well it shoots at 50', I've never shot mine beyond that 50'. That's all I've had for years, and they work perfectly fine for me. Should cost about $130.00 or so for the kit with a 10 round mag.
Dave Dow