Two variants of the RO933, a version of the M4 manufactured by Colt with a 11.5" barrel, appear in Battlefield Hardline: the Operator exclusive RO933 Carbine and the all class RO933 .300 BLK Assault Rifle.
— In-game description
The RO933 is a carbine featured in Battlefield Hardline, and is the first primary weapon available for use to the Operator kit for both factions. It has a higher rate of fire than the M16A3, at 850 RPM, and is an effective weapon at close and medium ranges, but has considerable drop-off at long range.
RO933 .300 BLKEdit
It is an integrally suppressed version of the RO933, meaning that it has a permanently attached Suppressor in its Barrel customization slot. As well, it fires the heavier .300 Blackout round as opposed to the normal RO933's 5.56 NATO, and is categorized as an assault rifle instead of a carbine.
The .300 BLK is a heavier version of the RO933, doing more damage and having greater range, but with heavier recoil and a slower rate of fire. Due to its suppressor being permanently attached, players will have to use under barrel grips to help compensate for the .300 BLK's heavy recoil as a Muzzle Brake or Compensator cannot be utilized. Unlike the normal carbine, Extended Magazines cannot be used on the .300 BLK.
- Like a few other weapons in the game, the RO933 has a secret reload animation where the character takes out the magazine and a third hand comes from behind with a full magazine, then puts it in with his left hand.
- The weapon in Hardline is a Colt Model 933, rather than the typical M4 carbine in other games.