I printed the double rib Hoffman ar15 lower (Polymaker PLA plus) and mated it with BCA .22 LR upper. Shot about 5 rounds through it. I stopped because it started to smell like burning plastic. Is that normal for the first few shots? Also, the .22 LR magazine is really loose in the magewell. Even fell out after one of the shots. Has anyone had this problem? Maybe I didn't screw the mag release button tight enough? Everything else seems to fit and move right. Thanks.
Plastic smell would be from the upper or ammo. My guess is the ammo. Mag well being too loose is odd. Have you tried fit with a standard AR mag? Scaling issues could be at fault, but should be visible via the front plates being really tight against the lower.
hoffmantactical Thanks for the reply. Standard ar15 mags seem to fit much better. I guess the CMMG .22 LR Mags are slightly smaller in dimension than standard ar15 mags. I've wrapped the CMMG .22LR mags with one layer of duct tape and that seems to solve the issue though it looks ghetto. I've never smelled burnt plastic with my .22 upper or ammo before. I'll keep shooting with the 3d printed lower and see what happens.
