Sherlock holding gun.
Bonus:
I think Sherlock uses a gun more than John does.
Also I see he sometimes switches hands.
Which would be kind of awkward if it’s supposed to be the same gun (like in the last two panels, notwithstanding that they usually use the Sig prop regardless of whether it’s supposed to be John’s gun or not at the moment), because they are actually built right- or left-handed, and if you use a gun in the wrong hand, you’re likely to get a hot bullet casing popping out into your face.
(Also the toggles for safety, clip release, etc. will be on the wrong side, but hot metal in your eye seems to win top spot in the Inconvenience Stakes. You know, they build them so the casings will mostly eject on the side meant to be facing away from the person, because somebody thought of this.)
Given Sherlock’s kickass aim with Mr. Smileyface (from behind his BACK; somebody’s been working on their trick shooting), I like to imagine that he spent a lot of time practicing with firing a gun because it seemed like a relevant thing for his work and he’s obsessive. But he never really fussed more than absolutely necessary with all boring the stuff about cleaning them, breaking them down, storing them, handling them safely…
Meanwhile John’s probably one of those types who used to get into contests with his fellow soldiers on who could break down and reassemble their weapon the fastest.