.Rez Editting Help

Hey I kinda new to this. So I was wondering if this is right if you take say the LAW model and swap it with an assault rifle model the result is a higher fire rate and recoil but no damage change? Also i was wondering when can you take the default m16a3 and swap it with an smg to achieve a higher fire rate or is this not possible because I have tried it my self and seem to have failed (the gun is invisible and cannot fire)

damage doesnt change
and m16 to smg has been done
also law to knife has been done