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The original Grendel, and what we now call Type II 6.5 Grendel, was designed to be used with a Grendle bolt, or.136 head spacing.
The patent was never released and to avoid any legal litigations, Les Baer Custom had adjusted 6.5 Grendel design of the barrel to make it .125 head spacing. We are now call it Type I Grendel. LBC has .295 diameter neck while Grendel has .300 diameter neck.LBC has a straight taper in the throat while Grendel has a compound taper.
The beauty is, LBC designed the .264 LBC cartridge to be completely compatible with a 6.5 Grendel. It also take 7.62x39 standard bolt, which in the long run gives a clinet greater flexibility to interchange their barrels on AR-15 platformwhile keeping the costs down.https://adventurefootstep.com/6-5-grendel-type-2-bolt-vs-type-1/