Problem with Grendel is there was and continues to be lots of confusion on bolt / chamber comparability
Short version of long story is : the AA 6.5 Grendel bolt is not the same recess (depth ) to bolt face as a 7.62X39 ...even though they share the same bolt face diameter .
Difference in depth is about .011 " . Grendel bolt is about .136"
Early days CSS started doing a 6.5Grendel but with 7.62X39 bolt depth ( they now have their 6.5CSS ) because they didn't want to pay royalties and buy the 6.5Grendel bolt for AA
They even changed bolt depth for the 6.5CSS in about 2006 ! Aaarrggg !
Fast forward to 2011 when AA submitted 6.5Grendel becomes SAAMI cartridge
In the 6.5 Grendel and variant world they refer to these are type I and Type 2 bolts / Chambers . Lots of information online
This is a good read : htt ://www.ar15.com/forums/t_3_121/696465_.html
Lost of confusion too form same manufacturers using both types over the years ( like Black Whole Weaponry )
Common versions are the 264LBC ( uses grendel depth bolt , slightly different reamer dim )
Good Points
Obviously the BC of the Sierra 123 Gr MK and Lapua 123 Scenars
Can't argue the external ballistics of the 6.5Grenel are not impressive
The quality of the brass is outstanding ( Lapua Brand ) . Norma brass is also outstanding , but doesn't have annealed necks like Lapua
The Hornady brass is just " good " but get what you pay for . Needs prep
Downside is you are always trying to recover all your brass since its spendy !
For plinker loads its very easy to make 6.5 Grendel case from 7.62X39 brass
My initial fireform load will cycle action
Scrap rate is surprisingly low ( less than 5 out of 100 split neck )
Parts for Build
I have built on Sabre Defense button rifle , Satern cut rifle , Satern Liberty ( 5R button rifle ...they make them for Brownells )
The one upper I kept was the Satern Cut Rifle .
Reloading
IF you decided to get all out on dies , like the Redding Competition , just make sure you get the VLD seating stem . You will put ring on those ###y Scenar / SMK bullets when seating
Also , Redding does not recommend seating compressed loads with their competition stems . Found that out the hard way belling out the seating stem .
They are cheap enough but something to keep in mind because if you don't watch for the belling of the mouth, it will eventually get to a point where you can't remove it from the floating sleeve
Biggest Downside
I would say the biggest problem with building a AR based Grendel is you really can't get the most of the cartridge unless you have access to over 200 yrd range
I build mine on what started to be a MK12Mod1 clone . Its probably my least shot upper since I only have up to 200yrds at local ranges
I find bench shooting my ARs are not as enjoyable as shooting steel with AR offhand ...but thats just me .
I have way more fun shooting Non Restricted precision rifle out to 500+
Not sure why you would build a bolt precision rifle on 6.5 Grendel when its easier to build 6.5Creedmore, 6x47 , 260 etc
I know there are Mini actions available ( Howa , CZ ) but not sure if the barrels are accurate enough to really make the 6.5Grendel shine at 500+yrds