Hey Dan,
The guys at 5th Group whomped this up for Afghanistan and the other Central Asian countries. The barrels would be in the 18"-20" range. Their goal was to get the most oomph possible out of the M-16 platform with the compromise caveat that it had to feed reliably out of the present magazines with only a slight feed lip modification. The other compromise is that they needed to keep the round count per magazine up there.
In a nutshell, the goal was to extend the effective range of the rifle by a 100 meters while retaining the option of high volume fire in close.
It does just that.
It is probably dead in the water as far as the military is concerned because it was developed by a couple NCO's and engineers for very little money, does what it was designed to do, and would be an easy conversion for the relatively small numbers of Spec Ops troops who would use it. The biggest reason it is dead is because of logistical issues. The rear echelon shoe clerks and blanket stackers aren't primarily concerned with winning wars or keeping our troops alive. They like to see big piles of the same things in warehouses in CONUS. Setting up supply and distribution for a new line of ammunition would cut into the time they reserve for office politics, and that ain't going to happen.
For many (most) of the soldiers the first rifle they ever shot was an M-16 in basic training. They have spent their whole shooting lives using that weapon, or variants thereof. The older guys eventually discover the joys of the 7.62x51. A lot of the older spec ops guys are taking over their own or their unit's special purchased SR-25's, AR-10's, or one of the new chopped and channeled M-1A's like the Troy Industries Rock Sopmod rifle.
JCN

You'd be right, if the 6.8 HAD a military status, but it doesn't now, and from the scuttlebutt I hear, never will have. It has NOT been adopted by any armed force, and it appears that it won't be.



The 6.8 is NOT based on the 5.56mm case, it is based on the old-time .30 Rem. case, which has about the same head as a .30/30 Win. w/o the rim. They had to shorten the case to make it fit the M16 magazine, neck it down to .270, move the shoulder, etc. So it gives 2800 FPS MV with a 115-grain .277" bullet.....

Dan, the 6.8 is a slightly shortened and blown out 300Rem case. HTH, Dutch.

lawndart and others in favor of: I don't doubt that people will tinker when "necessity" knocks, it's just not adding up to me. I do not know the specifics of real or planned performance but am making conclusions based on comments made about the concept. The 6.8 is based on the 5.56 NATO case, right? On the basic M16 chasis or something similar, right? Okay, but a superior platform for 300 meter success already exists if you feel you need more oomph out there. It's called an M14. It's the only thing the -14 is good for IMO. Personally I think the case capacity of the 5.56 is too small for meaningful gain with the 6.8 bore. You will likely have more retained energy at 300 meters with it, but at the cost of a higher trajectory and probably more drift. But, I haven't seen the numbers, or even explored them, so this is just a gut response. Operating pressure will have to be similar, maybe generating 2200-2400 fps? BC in the low .3 range? It just doesn't add up to me. Short of a full comp makeover the -16 has never been truly capable of meaningful effectiveness(accuracy/power) much beyond 300 meters anyway, so my thought is that rather than delude yourself by increasing caliber, why not approach it from the standpoint of an enhancement that is real? Velocity in the 2700-3000 fps range does have benefit and it takes a bit more powder to accomplish that than the 5.56 case can provide. 300 meter effectiveness is a chimera anyway, the only folks really needing that kind of performance being snipers, or others with the opportunity to take a steady rest and calculated shot, because most likely you'll only get one chance. JMO.

At the risk of sounding repetitious, the 5.56 NATO exists in the most effective man killing caliber that case can support. My observations are influenced by experience in Viet Nam, and I realize the rifle/cartridge has been changed since then. OTH, I've not run into a lot of people that used it in combat that would change a whole lot, at least not from that era. Don't know much about the "new and improved" models.

Blather OFF.