Reloading a Mauser C96 is certainly a 2-handed job! A drive check is appropriate here to avoid losing control of the vehicle, as I assume he is driving with his knee. As well, reloading is a full turn action so Perkins cannot fire this turn.
(As it was never specified what kind of Mauser Perkins possessed he has a vanilla C96. The full-auto
Schnellfeuer won't be invented for another 10 years, although he can easily pick up an artillery Mauser from the Gunmakers' Quarter!)
https://www.youtube.com/watch?v=yaaN5IWM2WA
It's funny in that the rules say it takes 1 round to exchange a clip, because (of course) they really meant detachable magazine. But the Mauser really does reload using clips! A clip containing 10 rounds is inserted into a guide on the top of the weapon and the cartridges are pushed down into the magazine, then the clip is removed.
Tony