Probably been done before but I did a shot at an intuitive weapon template.
Blue: Right Hand
Red: Left Hand (only use if you're doing some 2-handed weapon that doesn't mount other images like Guns Akimbo)
Black Cube: Directional indicator (remove it, just displays what's the front and what's up)
Width of the cubes: 0.14
Width of seperation: 1.05
https://hostr.co/Jr9kb4cCJqPd The Blender File
https://hostr.co/2gbLXzu6ef7E The DTS File
EXPORTING:
ALWAYS export as Legacy Mesh using Save As. If you Save on Blender rather than Save As, then it'll not export legacy.
If it appears wireframe in 2.49b and it is set to show solid faces, then you didn't export legacy or you simply used Save.