These are two rounds used in the AR15 platform. We took a few quick pics of this Bushmaster in a .270 cal. 6.8mm SPC (Special Purpose Cartridge) (the one with the red tip) and the standard 5.56x45 (.223) below it. The 6.8 is a bit larger so the 30 5.56 mags only hold 25 of the 6.8
This gas operated semi-automatic packs a bigger punch than our 5.56mm/.223models – a .270 cal. 6.8mm SPC (Special Purpose Cartridge) specifically developed for the military, but now available commercially. Velocity averages a bit over 2600 FPS (with Hornady 115 Gr.V-Max), and the heavier bullet weights deliver excellent terminal energies. The 6.8 mm SPC was developed from a .30 Remington case which is shortened slightly to fit the AR15 type magazine. Due to the “fatter” case diameter, magazine capacity in a 30 Round AR type shell is reduced to 26 Rounds, and 6.8 specific springs and followers are used. The bolt is also different - due again to case diameter (take care not to interchange a 5.56mm/.223 bolt with a 6.8mm SPC bolt). - Busmaster Website
It's a R.H. Twist – 1 turn in 10”
Here are a selection of AR ammo types. The 5.56x45 at top and bottom, the .7.62x51 (.308) second from top, 6.8 SPR below that and 9mm below that
The Bushmaster 6.8mm SPC Rifle and an AR15 SBR in 5.56x45 (.223)
RE: 5.56x45 (.223) vs. 6.8 mm SPC Rating: 5.00 out of 10
Fri. May 30, 2008 2: 42 pm
This round is a great idea, but too late. Besides the remote possibility of being fielded in some small units (CIF teams or CAG) it will never be adopted service wide. The 1 in 7' twist 5.56 barrel with a 55-68gr bullet has greater stability for long range accuracy. If your a varmit hunter you'll not see any benefit. The FN SCAR will be fielded by USASOC in the coming future, utilizing 7.62 and 5.56 variants. The logistics issues are one of the biggest block of the DoD accepting this round (and providing the downward pressure on prices through increased volume of sales for civilians). So if you want to spend your loot, go ahead. This round was the brainchild of 5th Special Forces Group and the Army Marksmanship Unit if anyone wants to dig more.
Unfortuantely, for the price of one fighter jet, our troops could have a weapon that actually stops the enemy. But we really need F-22 raptors right now to fight the booger-eaters.
RE: 5.56x45 (.223) vs. 6.8 mm SPC Rating: 5.00 out of 10
Sun. Mar 15, 2009 4: 26 pm
A lot has changed on the performance of this cartridge in the year and a half since this article was written. The magazine bodies and followers are different than those for the 5.56 is just one thing. The performance of the cartridge is getting better as it is realized that a slower twist rate of 1 in 11 or better yet 1 in 11.25 inches reduces pressures thus allowing higher velocities along with chamber specifications that are slightly different from the SAAMI spec. In many cases the accuracy is MOA out to 500 yards and possibly beyond. Realistically 6.8 performance surpasses the 5.56 at all ranges with a heavier bullet.
There is a lot of old misinformation out there on the 6.8 which is hurting the popularity. It makes the AR15 a viable hunting rifle for medium game and an excellent law enforcement round. Ammo is available from no less than five sources with premium hunting bullets or FMJ and everything in between. Factory ammo is available ranging in bullet weights of 85 grains at 3000 fps to 130 grains at lower velocity of course.
Lack of military adoption should not hurt this cartridge any more than the majority of cartridges that were not adopted by the military. This round has capabilities that people have not been exposed to yet and in a familiar package.
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