The sniper rifle should always do the same damage as the hunting rifle as long as they shoot the same cartridge. Period.
This isn't true in real life. Not only does barrel length contribute significantly to muzzle velocity, but the combination of bullet design/weight and barrel twist can affect flight characteristics and terminal ballistics. I.e. the same cartridge loaded with the same primers, powder, and bullets firing from two different rifles can have significantly different muzzle velocities, accuracy and terminal ballistics given a certain range.
As for F:NV, I gave the Hunting Rifle a slightly higher DAM than the Sniper Rifle/Gobi because its RoF is so much worse. When you move from tier to tier within the same weapon "concept", I think it's good to keep one statistic of the "worse" weapon superior to the better weapon. It means the weapon isn't instantly outmoded; there's still a reason to keep it around if you value that particular aspect.
I've already looked at the lever-actions and their RoF and AP costs were too low across the board. As I wrote earlier (?), much of the initial upscaling of the looping reload guns (.357 Magnum Revolver, Cowboy Repeater, Trail Carbine, Brush Gun, Lever-Action Shotgun, Hunting Shotgun) was because players here (Obsidian) disliked the long looping reload so much that other advantages of the guns were seen as not worth the hassle.
MadCat221, .45-70 Gov't is not an obsolete round in modern loadings. You certainly can't use it at long range due to the heavy, wide bullets most cartridges use, but at modest hunting ranges it will drop anything in North America including grizzlies and polar bears. .308 Winchester is designed for flat trajectory and tends to overpenetrate and have poor expansion at close range. It's pretty difficult (I won't say impossible) to model all aspects of gun/cartridge/bullet performance for a game (especially an RPG, where the character's stats come into play), but the .45-70 Gov't was selected as the top-end lever-action/revolver round because in modern loadings, at close range, it is an extremely effective round.