they collide each other because the polygons are not the same if you triple click it then they are all not selected why not try to make them same and turning on No self collison.
Forgot to say that i still dont know how to make them hold guns. The R4A1 buttstock does not break rule 5 because the maker of Flintblock Arms has not been making projects.
HOW DID YOU KNOW THAT I USE STICKMEN AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA oh wait ill make the algoboxians the human circle Pie head