Carbine wise the A91 is pretty beastly. I don't use sniper rifles simply because I suck with them, if I'm on a more open map I can more reliably down people with the RFB and a PK-A than a bolt action.
You need to play everything to its strengths though - you can work round some guns short comingsbut carbines in particularly are designed to be compromised guns. Anyone with a PDW will wreck you at close range and assault rifles will out damage you at long, and LMGs will wreck anyone at any range