Supersonic or Subsonic 300BLK SBR Defensive Ammo?

    300BLK SBR

    As much as I love the quiet bliss of subsonic 300 Blackout in a suppressed carbine, given the choice, I’d still pick a supersonic round for a defensive situation. In short, I’ll sacrifice ultimate sound suppression for nearly twice the muzzle velocity and energy all day and twice on Sundays. However, even most of the supersoninc 300BLK ammo is designed for barrel lengths of 9-12”, personal defense weapons (PDW) like the Sig Rattler, get the short  an end of the stick.

    I can’t remember where I stumbled across the debate: it was either in the comments section of our Facebook or Instagram pages or over on But the discussion centered on whether or not the best Subsonic 300BLK rounds are appropriate for defense orr if a supersonic round is required. The answer, of course, is dependent on multiple variables – distance to targets, clothing/body armor, etc all come in to play.

    There are those who will argue that subsonic 300BLK in an SBR is basically a pistol round disguised as a rifle. On the other hand, the criticism for supersonic 300BLK is usually “just use .308 already”.  My choice falls somewhere in between: the beauty of blackout is that allows the user to switch between ammunition that is built for different jobs. But is subsonic ever a suitable personal defense round?

    The answer is of course, yes. After all, if .45 ACP can be used in four inch barrels successfully, surely 220gr bullets in nine inch barrels can stop a threat if the shooter does their part. But the question gets more difficult as barrel lengths decrease. Barrels in both the Rattler and the honey badger come in at 5.5” or just over, leaving little room for a full powder burn let alone expansion at lower velocities.

    As a cure, Sig released a 300BLK SBR Elite Copper Duty cartridge specifically tuned for short barrels. For short barrels running supersonic loads, rather than igniting unburnt powder in your silencer, or worse yet, through your muzzle brake, Sig has a tailor made 300BLK SBR round for you. Details and specifications can be found below.

    Is the decision for either supersonic or subsonic 300BLK SBR ammo clear as day for you? Sound off in the comments section.

    300BLK SBR

    This supersonic duty round is engineered for reliable, controlled, 1.8x expansion, and superior feeding out of rifles with sub-9-inch barrels. The supersonic SBR Elite Copper Duty ammunition features an all-copper bullet and black oxide shell case to visually denote SBR capability.

    • CALIBER: 300 Blk
    • GRAIN WEIGHT: 120 gr
    • MUZZLE VELOCITY: 1897 fps
    • MUZZLE ENERGY: 959 ft-lb
    • MSRP: $30.95

    More information available on SIG’s site, here.


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    LE – Silencers – Science
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