this reply doesn't help me at all. i don't know if you mean that the model was left handed in the game when you wanted it to be right handed. or that the source model that you created of the lr300 was on the left-hand side.
anyway. all weapons built should be made as in the left hand side in your source file (i.e. in max, or milkshape or whatever you use.) if you don't create it on the left side then and on the right instead then your model will not show up properly in the game. this may be different for 1.6 i don't know but that's how i made all the models for czero otherwise the weapons would show up on the wrong side.