[Help] Model Swapping

OK well just to let you guys know
i have done model swapps before actually a lot of tiems
but this is the first time i got an error and yes i ahve tried many times too
to fix the error well the error is i get a white/gray/black screen
ingame when i use the weapon i cant fire but i can pick up otehr weapons
i tried a lot of ways well not a loot but 3

1: first tryi used only swapping the anibase and Pvmla

2: second try i switched all the files anibase, PVMLA, PVMLA_W and PVSMH

3: i tried Cross Modding then switching Textures


Tey both give me teh same result gray/black/white screen
the Gus i am trying to swap are

AK-47 to Scorpion
dont say you cant Switch AR to SMG's Cause
i Made an M16A3 to Mp7 MOD because and it worked
Any Help?
Sorry for the bad spelling i knwo how to spell it
just i type fast making me misspell alot

ty MPGH =D