[Help] Cross Modding

Well you know When you Cross Mod
and rename things
then you go ingame everything works
but the Gun looks like Shit
like its all deformed and stuff
well how do i make it better???
what texture files would i use

My example here would be

M16A3 to ACR Sandfire

it looks Like Uber crap
so how would i change it to look better

Well, I will tell you that it is a hex mod. Other than that, figure it out for yourself, choob.