From the information I've gathered, the Exotc snipers (Icebreaker, Patience and Time) both have a barrel perk that gives them more damage than Legendary snipers with the same impact and attack rating. The Attack rating tells you how well the weapon does damage against higher opponents (more of the damage it should do is actually done) and gives a small damage boost. While Impact tells how much damage is done per bullet. The higher the impact the more damage is done, but a weapon with a higher attack rating with the same impact does more damage. I've come up with a formula, but I don't know if it's completly accurate. For Legendary snipers with a max 331 attack rating and 25 impact it seems to work. Although sometimes it's a little off. The formula works better the other way around, if you want to calculate Attack rating compared to damage done. The higher the impact rating the lower the number (b) will get. I haven't been able to calculate everything yet. Dmg= 5,6101695 x Attack rating - 456,9661(b) * This is non-precision damage. Precision damage for snipers is the base damage x5. Y-09 Longbow Synthesis Attack 272 - actual damage 1069 - calculated damage 1068,9751 Attack 283 - actual damage 1127 - calculated damage 1130,7119 Attack 294 - actual damage 1189 - calculated damage 1192,4237 Attack 331 - actual damage 1400 - calculated damage 1400,0000