Give Zarinaea-D a try. Package at Gunsmith.
Version I have (on Titan) has the rolls:
SD Thermal
Hot Swap
Counterbalance
High Caliber Rounds/Braced Frame
Best roll in my opinion:
SD Thermal or SC Holo
Crowd Control
Counterbalance
High Caliber/Braced Frame
[spoiler]Gun is so good in pvp, I didn't want to post this[/spoiler]
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A even better auto rifle would be DoP or Vision Stone