Ok well this is rather easy--all you do is take your new models, and rename them...errr-here do this
take your weapon files,(usually consist of 3files per gun not including the ammo[clips])
Put the weapon files into the
valve/models folder.
Now... Open up a pak explorer(HLMV) and go to the weapons you wish to replace. Say you want to replace the
9mmAR with your new model...
Theres v_9mmAR.mdl
w_9mmAR.mdl
and two others,
open each model, then open your other models, now all you have to do is rename your new models to the correct, corresponding one. and thats
it.