I saw this piece earlier but it only occured to me now that the issue could be that the gun only recoils upwards. Guns recoil the opposite direction they fire in addition to, but not necessary, a little upwards too. It seems like common sense, but things are commonly forgotten during the pixeling process.

its still awesome :) keep it up

Thanks, I'll try to get that more accurate next time :)

the arm holding the grip of the gun should move back more .. from the elbow

I agree it would have needed some more frames to look better :)
However it's not a shotgun (it looks like it though) and doesn't need reloading.
It's supposed to be only the recoil of the weapon.
 

needs more frames its to fast looks like its jerking off the shotgun not reloading it .. hand should move back then forwards then shoot aswell :)