Here you see the empty .223 case, then cut down, necked to .30 caliber, and then loaded for the 300 Blackout.
I am in the final stages of testing the Barnes Precision CQB Patrolman’s rifle in 300 Blackout so I thought it would be a good idea to talk a little about this relativity new round.
The 300 AAC Blackout (or 7.62 x 35 mm) was created by Advanced Armament Corporation under the direction of Robert S. Silvers. The 300 AAC Blackout is very similar to the 300 Whisper which was developed in 1992 by J.D. Jones of SSK Industries. With only the 300 Blackout chamber is .015″ longer than the 300 Whisper. The 300 Whisper was originally based on the .221 Remington Fireball necked up to .30 caliber. The .221 Fireball has the same sized case head as the .223 Remington (5.56 x 45 NATO) so by cutting down .223 cases to 1.400″ and neck sizing them using 300 Blackout dies. This allows AR 15 lowers, magazines, and bolts to be used for rifles being built for the 300 Blackout. Both cartridges use the same reloading dies and data. Whether you can shoot 300 Blackout in a 300 Whisper and vise versa depends on who you ask. Myself, I always error on the side caution.
The 300 Whisper is somewhat of a wildcat cartridge and not listed under SAMMI specifications so variations can be encountered, some of which may exceed safe operating pressures of an AR-15 platform. When AAC began to develop the 300 Blackout the operating system of an AR 15 was the base of which the cartridge was centered around. The 300 AAC Blackout was submitted to SAAMI in 2009 and was approved January 17, 2011.
The 300 Blackout is somewhat of a duel purpose cartridge from light weight 110gr bullets pushed up to 2400 fps, to midrange weight bullets from 125gr to 155 gr bullets still pushing past 2000 fps, to the heavy bullets from 165gr to 250gr which can be loaded to subsonic velocities that work very well in suppressed rifles, still out performing any other subsonic cartridge at 200 yards. Up to 225gr bullets max out around 1400 fps still delivering a hard punch out of an AR 15 style rifle for closer distances.
The 300 Blackout is very similar to the 7.69 x 39 and 30-30 Winchester in performance but has a wide variety of bullets that are not recommended the tubular magazines of many 30-30 rifles. As I said earlier by keeping many of the dimensions of the .223 Remington parent case AR 15 lowers, magazines, and bolts can used for the 300 Blackout AR 15 rifles. If you already have an AR 15 in 5.56 x 45 or .223 Remington and a nice collection of magazines all you need is a 300 Blackout upper to use with your lower.
You can see the Barnes Precision CQB Patrolman’s rifle in 300 Blackout review here.