Anti-Materiel Rifle damage : 110.
Anti-Materiel Rifle crit damage : 190
Sniper Rifle damage : 62
Sniper Rifle crit damage : 124
Gobi Rifle damage : 60
Gobi Rifle crit damage : 120
What you gotta remember is the Hand Loader perk though.
With that you get access to;
.308 JSP - +50% damage
.50 Match - +15% dmg, -35% spread.
This puts the stock Sniper Rifle at 93 damage, none-crit.
AmR is at 126.5 none-crit.
i'm not 100% sure of how the bullet modifier effects crits, but assuming the modifier effects the crit. bonus damage aswell, this puts the rifles at;
Sniper: 186 crit,
AmR: 218.5 crit.
But when build optimally, your character will crit roughly 5 times more often with the Sniper Rifle, than with the AmR, putting the Sniper vastly ahead of the AmR. Not to mention the option for a silencer makes the Sniper alot stronger against groups of opponents.
Granted the AmR will hit harder w. the sneak crit. But every consecutive shots will be weaker, provided you've build your char to the 100% crit chance with. Snipers, either by the Build to Destroy trait, or by having 10 luck.