Help with weapons.lbt

i'm sure if you poke around in rez files there will be some gun with no pvmla_w or pvmla but its on cm_....something... my question is that how do you convert it to pvmla like a m134 its only cm_...something-... and 1 anibase and lets say you want it to change it to m9 and since m9 has pvmla files and 1 cm_ and anibase file how do you know which cm_... to change to pvmla or pvmla_w?
pls tell me if my questions are not clear

ps. im not trying to duplicate the superknife mod im just trying to give an example coz i came across some guns.

You don't have to change anything to pvlma.