Urbanman replies: The 6.8 SPC (6.8 x 43mm) due to it’s overall length and relative low chamber pressure made the M16 or AR platform adaptable to this cartridge. Although the bullet diameter is smaller, I tend to think of this cartridge like a the M43 AK round (7.62x39mm).
It is a good stopper and was developed and pushed by elements of the Army Special Forces community to replace the 5.56x45mm (.223 Remington) as small groups of Special Operators would find themselves in a "target rich environment" and the 5.56 was failing to put people down for the count. This was largely due to the SS109 bullet - steel core penetrator, which had too much penetration and did not leave all of it's energy in soft skinned targets.
The 5.56x45mm standard military round in the 62 grain SS109 configuration has a muzzle velocity of approximatley 2,700 fps depending upon barrel lengnth. The 6.8x43mm SPC round with a 115 grain bullet travels at 2,800 fps. More diameter and weight, and more velocity, give the 6.8mm SPC the edge of which round is a better stopper.
I would not begrudge anyone going to the 6.8mm round in an AR platform. The considerations would be ammunition availability and price - certainly much, much cost involved than stocking the abundant .223 Remington. The cost difference between equal amounts of rounds has to have the 6.8mm SPC costing twice as much if not more. Are you going to be to stock 4,000 rounds per gun? That's my base figure for ammunition on hand for each main long gun. I'll stick to my AR platforms and the 5.56x45mm round.
The bottom line, as I am reminded by readers all too often, is to have a long gun for these lawless survival environments; be able to use it well; and have sufficient ammunition for it. Sounds like good advice to me.
