Depends on what you are thinking about inregards to porting a weapon. If you already have the original 3dsm model and it's made to specs then I wouldn't call it porting, it will just be different export settings in order to get it into a new engine. If it's a model not made to current specs then it's almost easier to start over again from scratch. I tried re using some older models for some of the GB content and it turned out to be a royal pain in the rear, just having to rework a model not made with animations in mind into one that could be animated was a headache and a half!
Case in point was the original M4 model I shipped to John, it was a quick and dirty rehash of a VBS1 model I made a long time ago, well before I started using normal maps and making highpoly stuff to extract a normal map from. That model evolved from the VBS1 specs into almost GB spec when I used it in my GRAW1 mod and later was somewhat reworked again before I shipped it to John. Unfortunately it just could't hold up compared to later models made especially for GB so I had to go back and redo just about the whole thing all over again at a later date, that time around using a properly made mesh and highpoly model to bake my normal maps from. Think I showcased the highpoly mesh for that one in the donators section once upon a time, at it's most detailed state it was even to high in polys for my computer to render!
Even so I think there's still one trace of the original model and it's reference that carried over into the current GB M4 that isn't accurate to real life. You really have to be a weapons nut to pick up on it in it's current configuration though, asfar as I know no one has noticed it yet or atleast haven't commented about it yet