As seen in the video, the gun starts to count wrongly, from 18 to 16 bullets, but after 3 shots given by the player, and then after a reload, it begins to count the bullets the right way, going from 18 to 15 bullets, which also have shoot once more only 3 times:
I don’t know if this also happens with the bazooka, but i guess it does, perhaps after testing it i can say if is true or not at least.