I apologize for the first review I left but it was out of frustration that this kit wouldn’t not run after so many attempts and weeks. Fast forward this 380acp build kit is finally operational and am loving it with how accurate and how hard hitting this little mouse round is. I found that the included 9mm upper receiver did not allow enough room for the spent round to leave the receiver after it was extracted and would bounce around while getting caught by the cycling bolt. Another thing I did was polish the barrel chamber so there was zero chance of any hang ups. And the last thing I made sure that there is no slop/wobble of the (mean arms exomag) magazine in the magwell. Ammo used was 380acp 100gr re-man