well what i would do is to get as many refrence pics as i can., and depending on your weapon, i would get a crap load of cardboard and i would mane the outline of the weapon and build it bith layered card board, but if its a weapon like the siper rifle. i rould use layering for sime parts but i would make it hollow. but reanforce it with a bit more resin. resin the weapon once you have made id. and i would put bondo body filler on it to harden it up and ic will give you a layer thick enough so u can carve detail into it with a dremel if u want. hope this helps!
