ORIGINAL: ShatoDavis
It was designed to add more stopping power to the M16. The guidelines where for it to be a simple conversion in the M16, Ie barrel swap. That being said it had to use the same bolt. the 5.56 Nato has a .378" case head, so the new round must as well. So what you have is a 223 necked up to accept a 270 cal bullet.But, I would probably be searching for a M14 shooting 7.62 Nato, also known as the 308, which is a far better round.
This round was intended to provide better stopping power at greater ranges than the 5.56mm NATO. It does this. It is also intended to be used in an M-16 based action. However, it is NOT simplythe 5.56mm NATO necked up to .270. It is the
.30 Remington Rimless case of the early 1900's, shortened and renecked to fit inthe M-16 magazine, and sized to hold a 115-hgrain .277" bullet.
The .30 Remington has a head diameter of .421", and is essentially a
RIMLESS.30/30 case. So an M16 will need a different bolt face, as well as a new barrel, to use the 6.8 SPC.
There is NO WAY this6.8 is as effective as the 7.62mm NATO round, but it has to be an improvement over the 5.56mm. As far as sporting applications are concerned, it will no doubt kill deer. But is it BETTER (or even equal to) such little rounds as the 6mm Rem. or .257 Roberrts (let alonesuch things as the.270WIN., 7X57mm or .280 Rem.)?? I really doubt it!