I think this has already been done quite a few times. starting with a guy called Thor who when he threw his hammer down the bad guys dies but the hammer is right there in Thors hand and if you think about it a revolver looks a bit like a hammer
A piece of whatever threw him back in time broke off and came with him, he jerry rigs it to the magazine with wire and whatnot. The character get infinite ammo because it keeps cycling in the same rounds from the past. Ammo problem solved.
I do think a pistol that shots long range smart bullets, after hitting the target they return back, like a boomerang.... keeping the Australian link alive
That way you need a bullet resizer and a bullet pointer.