6.5 Grendel is an excellent cartridge. I would suggest you take a look at 6.8spc. The chambers are almost all spec'd to SPCII now (Remington drawings were incorrect on the original chamber) and the twist rate of most barrels is not correct. AR Performance and Buffalo make a superb upper. Rock River, STAG, LMT, etc... and many others are out there with good quality as well. If you have the cash Noveske has an excellent spec'd Lothar barrel to offer.
6.8 is excellent on deer and there are a lot of inexpensive 270 cal weight bullets out there from 80gr to 140gr. You should be loading your own if you wan't either of these calibers. Silver State Armory has top brass. Hot loads will go 12 loadings no problem. They are the mil supplier of 6.8.
I have been in on the 6.8 since the beginning. I liked it enough in my AR's I made one off a Stiller Predator (bolt) action. No recoil, sub moa 5 shot AR is not anythign difficult, and plenty of magazine support and loading components, as well as tons of re-barrel choices.