Thanx, Mr. Lee.
5sub:
Here is what I know and seen.
The new mags are steel. They are longer than the current M16 mag, approx. 3/4 of an inch longer, depending on how you measure them. All the followers I have seen are black and the hump on top is boxier, as oppose to rounded type on the M16 5.56 mag. They are appear parkerized or some sort of phosphate finish. Retro fitted 5.56 mags work as well, just replace the follower and spring (the replacement of the spring maybe optional). They are noticably heavier than the aluminum M16 mags. The aluminum M16 retro fit mags, as Mr. Lee stated, hold 28 rounds. Some difficulty is encountered when trying to load the mag in a gun with the bolt and carrier forward, so, 26 or 27 may be the realistic number. There appears to be plenty of material in the follower, so maybe a slight mod could be made to add a bit more space.
The rounds that I have seen were made by two different manufacturers of which one is Remington. Some of the head stamps say 6.8 and others say .30 Remington.
Some of the bolt and bolt carriers appear standard M16, that have been modified, and some are of new mfg. The bolt face has been opened to accept the 6.8/30 Rem case. The new type carriers have three holes in the cut out area as opposed to two on the M16 type carrier. Also the gas relief hole has been moved about an 1/8 inch higher. These mods could have been made because the primary use of this rifle will be Spec. Ops, and therefore a lot of suppressor use(this is pure, hopefully rational, speculation on my part.) I do not know this for fact.
I have heard that PRI is selling mags and uppers for this caliber. This maybe rumor, but I'm sure you could find out on their web site.
I'm sure there will be lots of pros and cons, and lots controversy on this caliber and rifle. Not wanting to be left out, I'll start the ball rolling...."It's HEAVY, way HEAVY"