Oh, by the way, on magazines, check this one out--they are in the second generation and reviews are pretty good.
http://www.primaryarms.com/rze-unimag-multi-caliber-magazine-rze-mag-001b
I am probably going to try one but my research indicated that ASC makes good Grendel magazines--I also think that ASC did make Midway's AR-Stoner brand mags for the Grendel but that could be out of date.
PRI and Barrett are the 6.8 SPC champs for mags that work. BTW, If you've never tried them, Primary Arms has great service, fast shipping, and really good sale prices.