A fair amount of you have asked me about the reasoning for Discreet Ballistics having two different loads for 300 Blackout. We make a Pistol/SBR load which is optimized for barrels between 7-11” and a Carbine load which is optimized for 16” barrels. The reasons we offer these two different loads is due to the inherent velocity loss encountered with when shooting a load designed for a 16” barrel out of a shorter barrel. This velocity loss can be as much as 200fps. While this lower velocity doesn’t necessarily make the bullet any less accurate it does have a couple of downsides:
- The lower the velocity the longer the bullet stays in flight. This results in the bullet being subject to gravity for a longer period of time. If a rifle is zeroed for 50 yards shoots a round with a muzzle velocity of 1050fps the 190gr bullet will exhibit a 6.7” drop at 100 yards. Conversely, a round fired with the same 50 yard zero with a muzzle velocity of 900fps the 190gr bullet will exhibit a 9.5” drop.
- Energy delivery will also suffer with a lower velocity. Using the same numbers the bullet with a muzzle velocity of 1050 fps will have 422ft/lbs of energy at 100 yards while the bullet with a muzzle velocity of 900fps will only have a 322ft/lbs of energy at 100 yard. These numbers are particularly important for putting down game.
Ballistics Chart for bullet at 1050fps Muzzle Velocity (courtesy JBM Ballistics)
Ballistics Chart for bullet at 900fps Muzzle Velocity (courtesy JBM Ballistics)
So why don’t other subsonic 300 Blackout manufacturers make two loads to accommodate both long and short barrels? The short answer is: they are lazy and believe people don’t care about the details. The difference with Discreet Ballistics is that we know that there are always folks out there that want to get the optimal performance from their rifles no matter which caliber they’re shooting.