Мафия 34. WildWestSteamPunk.

Also, a Mosin rifle, if I remember correctly.

7.62 caliber – it was, and still is, a fairly common caliber. There's quite a lot of weaponry with that caliber. Probably to ensure compatibility.
If it's about the caliber, let's focus on those who have a clear mention of weapons.
No, we can also consider Nebo, but next, I suggest Rimpel. He has a Winchester.

And who started the idea that it's about the caliber? It says there are scratches, and imagine their thickness – what could have caused them? And where are they – on the door frame and the table. Maybe it's a hint about what was used to break into the door (to enter) and the table (to get money/valuable papers, or whatever else might be in the table).

P.S.
I looked at the mental avatar – there's a robot rabbit. I don't remember from the cartoon, but it seems to have 4 fingers, 1 large one, and three – that's what it could use to scratch the door. And 2.45 – claws.
And in general, in the cartoon, this rabbit is a Terminator-welder of the 5th level xD