Advice on buying a grendel upper for a Noob!!

[VASCAR2]

One thing to be aware of is which bolt is used with the barrel. Some manufactures are using 7.62 X 39 bolts (model 1 sales 6.5 CS, Kies 264 LBC) while others are using AA bolts which are recessed. The AA bolt is supposed to be stronger than the 7.62 X 39 and usually not interchangeable. Ive also read where AR precision is going to use a super bolt with a different barrel extension. I personally wouldn't buy a barrel for 6.5 G/264LBC without a bolt matched to the barrel. My personal choice was a barrel with AA 6.5 Grendel bolt. The AA 6.5 Grendel bolt is also the same bolt used in the 50 Beowulf and both use a standard AR 15 bolt carrier.