Might want to check into the availability and cost of ammo and brass before buying something you can't feed.
Well I really like my AR in 6.8 SPC. I am actualy on my second carbine (first one was in the M4 style, and went to someone who wanted more than I) and I have all the parts to build, a 20" hbar.
For Ammo, I have it on good authority that any dealer that carries remington ammo, should be able to order it in. It may just be a wait and see game. Last time I checked, Bashaw sports had a goodly amount, and said they would be able get more for those who were "prepared to put there money where theif mouth was."
From a reloading perspective.............
Bullets, are simply .277 diameter (yes the same as 270 win) from 90 to about 115 grains.
As for brass, last time I checked it was simply a phone call to Epps to get some, and they seemed to have no issue getting me the 1k I requrested, at a price far less than the $1.00 per peice of 6.5 grendel, and far less hassel then forming it for the 300 Whisper.
I like this cartrige, and it can simply be summed up as
"80% the power of 308/7.62, with only 20% more recoil than 223/5.56 Nato, all in an AR-15 footprint"
To be honnest I like and respect what this cartridge can do. Now I truly get tired of those who, in broad strokes, simply dismiss it out of hand, with out any first hand practical experience, either in shootig, feeding, or reloading for it.
As has been noted, the 6.8 SPC seems to be much more popular than the 6.5 Grendel (or what ever you want to call it to avoid paying royalties to Alexander arm). Thats because major manufatures are building carbines (Noveske, RRA, & Stag come to mind) and Ammo (Remington, Blackhill, and there are rumors about Hornady). The same can not be said for the Grendell.
We are all entitled to different opinions, and I support that. However my suggestion is don't knock it until you actually try it.
YMMV
regards
AbH