The 6.5 Grendel II chamber has a parallel rather than compound throat. It has a .120” throat and a .300” neck. This has become the most commonly produced 6.5 Grendel chamber and is what Grendel Hunter uses.
The SSAMI Grendel chamber has a compound throat, .300” neck and conforms to the standards published by the Sporting Arms and Ammunition Manufacturers’ Institute.
.264 LBC is a Grendel clone with a .120in throat and .295neck.
A Type I bolt, also known as the 7.62×39 bolt, has a bolt face depth of .125” and is used with some Grendel variants. The Type II bolt is the bolt originally designed for the 6.5 Grendel and has a bolt face depth of .136”. It is used with both the SAAMI Grendel chambers and the Grendel II chambers.
Grendel Hunter handguards will fit any mil-spec AR15 upper receiver and should fit nearly all billet receivers as well.