Magnum Skill?

I know the magnum is one of the best weapons in this game (imo), some of you will agree with me and also might think it’s op. The thing is the gun can be very useful I just have a question.

How many shots does is it take to break the opponents shield? I noticed that when I’m using it and just firing it I break the opponents shield where then I aim for their head to finish them off, I just haven’t noticed how many bullets I used on them before finishing them off with a headshot. Does anyone know?
Thanks!

4 to break shields, 5 to kill (all headshots)

> 2533274852660538;2:
> 4 to break shields, 5 to kill (all headshots)

Alright Thanks.