I used to work on miniguns in the military and I can tell u that the ammo is fed into the back section that little tube that sticks out of the side on your model it's called a feeder and ammo is fed in through that and into the bigger gun housing chambers the shot out the barrels. There is a chute that looks like a bunch of linked [_] Where the ammo is fed through. I know this may sound strange but if you need more then I can even give you some detailed pics too. I worked on many small arms including miniguns 50 cals m-9 ect....

No need for 3d letters just make them in bryce using the terrain editor just go in photoshop and make a black and white pic, (letters white and black back ground any font you want). Then open the terrain editor in bryce and import the pic and your terrain will be the 3d letters just clip off the bottom and you can add textures animate them and also export your letters.

Attached Link: http://www.3dlinks.com

Apply the transmap in the transparency channel then put a dot in that channel to see the maps effect.

Need more information to in order to fully pin point your problem is this a OBJ or DXF or some other format.

For Video editing you should try Adobe premire 6