They work well enough. I have a CMMG kit with the BDM mags. It's cheap to shoot 22LR, but the precission is TERRIBLE. I went to Canadian Tire and Walmart and bought every type of ammo they had to see which would perform best in my rifle. Out of the six (or maybe more, I can't remember exactly) different types I tried, none were great. The tightest I could get the groups was 2" at 25m. That was in both a 1:7 twist 16" barrel and a 1:9 twist 20" barrel. What I'd really like to know is where to get a proper 1:16" 22LR barrel to build a dedicated upper from. I see Brownells has then, but they're $139, so that's not getting over the border...