Project made this weekend, tested on godot. Works pretty fine. Included 3 blendfiles:
Mosin: contains handpainted mesh without modifiers.
Mosin_Rig: Mesh with vertex groups and linked armature.
MosinV2_Animation_Rig: Extra file with basic animations. I did imported the project to godot and works perfectly fine. Obviously the rig needs a little bit of tweaking.