USAF_Vet
Member
Does a 9mm AR upper require M4 feed ramps? I'm thinking probably not, but want to make sure before I go and buy a receiver I may need to mod.
Lead filler? Bore out the carrier and fill it with lead? More weight, stiffer spring, shorter travel. It might be tricky to work out, but there is no reason the travel for a 9MM AR blow back action couldn't be shortened.mass is going to be an issue.