Les Baer Custom designed the .264 LBC cartridge to be completely compatible with the 6.5 Grendel, and our head space gauges are marked with both cartridges.
The LBC has a .295 diameter neck, while the Grendel has a .300 neck.
The LBC has a straight taper in the throat, while the Grendel has a compound taper in the throat.
The LBC uses 7.62×39 AR bolds with .125 head spacing, which is the standard head spacing for all AR rifles and most modern bolt actions, while the original Grendel used a Grendel bolt with .135 head spacing.
We originally made rifles with the standard head spacing (.125”) which we called type 1 and a second head spacing (.135”) only for the original Grendel which we called type II. Given the demand for standardization and lack of sales the type II head spacing has been dropped for 2017.