You need a cripple stock gun.
Edit: well shit, I just saw that you posted this video right after I commented lol
You need a [cripple stock gun](https://m.youtube.com/watch?feature=youtu.be&v=_mcVFrk7omk).
Edit: well shit, I just saw that you posted this video right after I commented lol
But I did shoot well enough in basic to earn a marksman ribbon. Something like 47/50 shots, but I could have gotten expert it seems, lol