Compositing Test

I  downloaded an M4A1 model and recorded myself miming a firing position. I put the video into the viewport background on Max then animated the M4A1 to the video. 

The render of the M4A1 was still slightly out in terms of spacing, but keyframing within After Effects sorted that problem.
I did a botch job of Masking, just to get a rough idea of how it would look.
In a final piece I'd make a much more professional job of it, but I wanted it done quick for the blog.

This technique will be what I use in the final piece for the Hover board.
Taking live action skater, compositing the hover board into it, covering the real skateboard, with a composited background (the initial shot will be done on a blue screen).