Slam firing except when on safe????

Alright, today I got a couple of upgrades and a new cylinder for my javelin m24, but it seems that when the guns safety is off, it slam fires. But, when I put the safety on it magically doesn't slam fire. Also it isn't fault of the cylinder, because this was still happening with the old one, which snapped in half. Any tips on how to fix this? I cant seem to find any info on it either. Please help!!!