Hello, and welcome to the Reloading Podcast here on the Firearms Radio Network.
Tonight the guys are Talking with Miguel from Freedom Seed Brass.
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Hello all... loading 44 mag and I'm needing some piece of mind with a question that's bugging me....Book says shot out of 8 inch barrel should be 1340 fps, when I shoot out of 18inch Henry big boy. I get 1560 fps average. I fully understand faster velocity for barrel length. But my question is does it change pressure or is pressure consistent with lead data no matter barrel length?
Cartridge Corner Notes:.300 AAC Blackout
The .300 AAC Blackout (designated as the 300 BLK by the SAAMI and 300 AAC Blackout by the C.I.P.), also known as 7.62×35mm is a carbine cartridge developed in the United States by Advanced Armament Corporation (AAC) for use in the M4 carbine. Its purpose is to achieve ballistics similar to the 7.62×39mm Soviet cartridge in an AR-15 while using standard AR-15 magazines at their normal capacities. Care should be taken not to use 300 BLK ammunition in a rifle chambered for 7.62×40mm Wilson Tactical.
While 5.56×45mm NATO has enjoyed widespread acceptance in military circles, the nature of the missions encountered by some special operations groups often demand a round that provides better performance than that available in the high-energy standard velocity rounds and subsonic performance greater than standard 9mm (the ubiquitous pistol round also commonly used in many SMGs).
To satisfy this need, AAC developed the 300 AAC Blackout in cooperation with Remington Defense—under the direction of AAC's Research and Development Director Robert Silvers and with the support of the company's founder, Kevin Brittingham.
Meeting these goals allowed the development team to negate many of the perceived drawbacks inherent to other large caliber cartridges used in the M4. Colt Firearms and other arms makers had previously chambered AR-pattern rifles and carbines in various .30 caliber rounds but encountered problems. In the case of the 7.62×39mm, its relatively severe case angle caused feeding issues unless specially modified AK-47 magazines were used, and even then results were unsatisfactory Modified bolts were also needed owing to its larger case head diameter. Rounds such as the 6.8 SPC and 6.5 Grendel had similar part-interchangeability issues but did allow for the use of the standard M4/M16 30-round magazine albeit with a reduced capacity.
300 AAC Blackout rounds shot from a suppressed M4 Carbine.
Wildcat cartridges such as the .300 Whisper series addressed these issues, but their widespread use in single shot handguns and lack of industry standard cartridge dimension meant that a great number of the popular loads on both the supersonic and subsonic end of the spectrum were less than ideal in the AR pattern weapons. Many of these rounds required an excessively long overall cartridge length that would prohibit feeding in a STANAG magazine while using powder charges that were not compatible with the pressure requirements of the M4 carbine. This was particularly noticeable when using subsonic ammunition in conjunction with a suppressor as short stroking and excessive fouling would occur similar to that which was seen in the earliest variants of the M16 in Vietnam.
By keeping the M4/M16 in mind as the primary host during load development the designers could work up a host of cartridges that not only satisfied the ballistic requirements set forth, but also ensured mechanical reliability with the fewest changes to the weapon itself—with only a simple barrel change necessary for complete conversion.
Robert Silvers, director of research and development for AAC said, "We started development in 2009, but most of the work was done in 2010. A military customer wanted a way to be able to shoot .30-cal. bullets from an M4 platform while using normal bolts and magazines, and without losing the full 30-round capacity of standard magazines. They also wanted a source for ammunition made to their specs. We could not have just used .300-.221 or .300 Whisper because Remington is a SAAMI company, and will only load ammunition that is a SAAMI-standard cartridge. We had to take the .300-221 wildcat concept, determine the final specs for it, and submit it to SAAMI. We did that, and called it the .300 AAC Blackout (.300 BLK)."
300 AAC BLACKOUT was approved by SAAMI on January 17, 2011.
On October 23, 2011, SSG Daniel Horner of the USAMU used 300 AAC Blackout to win his 4th USPSA Multi Gun National Championship.
Place of origin United States
Parent case .221 Fireball/.223 Remington
Case type Rimless, bottleneck
Bullet diameter 0.308 in (7.8 mm)
Neck diameter 0.334 in (8.5 mm)
Base diameter 0.376 in (9.6 mm)
Rim diameter 0.378 in (9.6 mm)
Case length 1.368 in (34.7 mm)
Overall length 2.26 in (57 mm)
Rifling twist 1:7
Primer type Small rifle
Maximum pressure (SAAMI) 55,000
Maximum pressure (CIP) 53,000
Maximum CUP 52000 CUP
Bullet mass/type Velocity Energy
125 gr (8 g) OTM 2,215 ft/s (675 m/s) 1,360 ft⋅lbf (1,840 J)
220 gr (14 g) OTM 1,010 ft/s (310 m/s) 498 ft⋅lbf (675 J)
78 gr (5 g) Lehigh Defense CQ 2,800 ft/s (850 m/s) 1,358 ft⋅lbf (1,841 J)
90 gr (6 g) Barnes OTFB 2,550 ft/s (780 m/s) 1,300 ft⋅lbf (1,800 J)
110 gr (7 g) Hornady Black V-MAX 2,375 ft/s (724 m/s) 1,377 ft⋅lbf (1,867 J)
Test barrel length: 16 in
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