Advanced rifling increases damage falloff ranges by 30% on SMGs, stacking with the Suppressor, having a net 9% range decrease. Advanced rifling doubles the maximum damage ranges of all rifles, except the BAR, being a very effective attachment to combat targets at long range when combined with an Reflex Sight or 4x Optic and Grip, however few maps have such ranges. Only the PPSh-41 and (to lesser degree, 3-shot range unaffected) MP-40 SMGs see any worthwhile improvement in the SMG category. For hardcore, only the M1941, STG44,Volkssturmgewehr, Grease Gun, MP-40, Sten, Luger, Walther P38, Reichsrevolver and (to lesser extant) BAR see any improvement. Shotguns see a decent minimum range increase of about 10%, allowing the player to damage targets at further ranges, however you should not expect one shot kills due to the pellet spread (with obvious exception to hardcore modes).