LOL I know the guy that made that gun/took that pic.
IT'S A JOKE!!
Look at the cocking handle slot: guess what? IT's DONE WITH A SHARPIE MARKER!!
Also note the barrel is so short that the tip of the bullet is sticking out.
For you thinking we were taking it seriously. Though it would have been pretty cool as a just because project. Probably have to use a locking wedge from an MP5 though, wouldn't get much pressure with that short of a barrel.