First off let me say this is more fun than any one person should be allowed to have!! These will be banned soon!!! So I picked up a CMMG .22lr conversion with one 30rd mag and one 30rd BlackDog mag. I put it into my Stag AR15 with a .223 upper and proceeded to plink away. I lubed the .22lr bolt with some CLP before inserting it into the receiver. It functioned great with Remington Thunder Bolt and CCI MiniMag. I easily put through 200rds. I had heard it was better to get a dedicated upper, but for ~$150 this little kit is really cool! Accuracy was fine for plinking at 25-50yrds. My scope is zeroed for .223 and It shot a little low with the .22lr ammo, about 2 ticks on my scope. If you are on the fence deciding whether or not get one of these, I'd recommend it for the money. ~$150 for kit, two 30rd mags from Botach Tactical.