During the escape from the Mexican gun deal, the damage to the station wagon changes between shots.
When Jax is kidnapped at the lights, the van changes between shots. The shots when he is pushed into the van is an older van.
When Nero storms his gangs clubhouse, he pulls out a small shotgun and shoots a gang member, we then hear the familiar "clack-clack", of the action on a pump shotgun being racked. The shotgun he carries is an over/under, which only holds two shots, and does not have a pump.