As industry positions and prepares for the expected imminent release of a request for proposals for a potential M4 carbine replacement program (see “U.S. Army Looks for New Carbine Options,” posted June 1, 2010), some activities are expanding potential caliber offerings.

Although U.S. Army planners have made it clear that potential carbine replacement options will not be limited to the current 5.56 mm design, mid-December saw many interested companies accept a government opportunity to participate in a “familiarization shoot,” conducted at an independent testing lab, with government-provided M855A1 rounds (see “Full Rate Production Begins on Enhanced Army 5.56 Round,” posted on Nov. 15, 2010).

Describing the event, U.S. Army representatives noted, “The intent of the event is to provide vendors an opportunity to better prepare for the upcoming carbine competition. This will be particularly valuable for those looking to compete a 5.56 mm system. This shoot represents the first chance for our industry partners to see for themselves just how their weapons perform when using the powerful new M855A1 Enhanced Performance Round [EPR].”

“The carbine competition itself will be non-caliber specific,” they cautioned, adding that vendors not competing 5.56 mm weapons systems were still encouraged to participate in a parallel “compatibility check” between their weapons and under-barrel attachments like the M26 Modular Accessory Shotgun System and M320 grenade launcher systems.

In addition to the current 5.56 mm and increasingly popular 6.8 mm designs, one of several “dark horse” caliber options that might join any upcoming carbine competition is the 300 Blackout (300 BLK) 7.62 x 35 mm round developed by Advanced Armament Corporation (AAC).

“What’s the complaint about 5.56?” offered Mike Mers, AAC sales representative. “The complaint is that they would really like a bigger, heavier bullet with more knockdown power. Now, I’m not talking bad about other people’s stuff, but if you go to 6.8, you have to open up the bolt. We know that the locking lugs can shear off an AR-15 or M-16 platform in 5.56. Now, if you make that bolt face larger, you have less cross-section, and the locking lugs are going to break. So we don’t think 6.8 is the answer. Also, it drops too much.”

He continued, “Now, what’s the problem if you go the other way – to .308? Well, it’s really heavy. It’s got a big recoil with a big flash from a big gun.”

Acknowledging that other cartridges have done similar designs in the past, he offered AAC’s 300 BLK, explaining, “From this point back it’s 5.56. So it takes 5.56 bolts. Also, this comes out of a regular magazine, so every Army M-16 magazine is now a 300 Blackout magazine. The forward part of the cartridge is .308. That’s a .30 caliber bullet.

“This one happens to be a 220-grain subsonic bullet,” he added. “So now you’ve got subsonic bullets that will cycle the gun – from ‘box in’ until the last round – with functionality at 100 percent. Next quarter we’ll have law enforcement ammo. But here’s the thing: We can throw a 110-grain bullet out of a 16-inch AR-15 about 2,400 feet per second. Talk about lethal. It beats 7.62 x 39 across the board. Depending on the ammo it will also beat 6.8. A lot of guys will say, ‘You know, if you load an 85 grain bullet in 6.8 …” Well, you can put a 77-grain bullet in 5.56. So why not go to a .308 projectile and 5.56 brass. We just ‘neck it down.’ That’s all it is. When we’re talking about hunting or military, where you actually need to shoot something to kill it, a 110-grain bullet at 2,400 feet per second is awesome.

“Now, for tactical applications, you could simply switch magazines and you could have 220 grain subsonic bullets. Now, if you’re doing an entry, you can put a silencer on and do it all subsonic. We’re a silencer company so we like that subsonic application,” he added. “With a silencer we can make it as quiet as an MP-5 SD. But if you get into a firefight you do a simple mag change and now you’re engaging targets out to 300 meters.”

Remington Arms Company, Inc., which acquired AAC in late 2009, is one possible candidate to offer a 300 BLK option in the upcoming carbine competition.