Can't 100% confirm but I am reasonably certain that the sniper rifle's damage scales with your accuracy stat.
My reasoning for this is that usually it cannot 1-shot most enemies past floor... 3 or so. However, in one run as Marine I had found a muscle relaxant and from then on the sniper rifle was able to one-shot-kill just about every single regular enemy I came across with very few exceptions - those being the big skeletons with the bullet arms in the forge, and leadbulons (probably because they catch fire when they lose all their HP and gain some health back)
If possible I'd like some others to confirm. It might actually just scale in damage due to other effects, since I think shotgun coffee also made it hit a bit harder. Not sure. Azba (talk) 22:58, 9 April 2016 (UTC)