Although Aziel had no real hands-on experience with using or even training in the traditional sense in using guns prior to this event, with all the 'healthy donors' that were so kind to provide their memories and several lifetimes of knowledge that he absorbed and processed he was by no means a novice.
Though he still lacked experience, he knew the theory and was aware of how to aim whilst still not forgetting the heavy recoil such a powerful gun would emit. He was also confident in his arm strength to endure such a sudden pressure without issue.
Aziel aimed the gun a bit lower this time around so as when the recoil kicked in and subsequently raise the barrel due to the force behind the shot, he would still be able to land the shot on the head of these infected.