As of 7-12-16 the above is still correct. Any true 6.5 GRENDEL barrels will be furnished with a chamber ONLY compatible with a bolt depth of 0.136. To determine this put the tail of your calibers in the bolt face and push down. You should have either 0.125 or 0.136 nominal.
Any FACTORY BRASS cased 6.5 GRENDEL ammuntion can be fired in the 264LBC chamber. Some steel cased ammuntion may be too tight to be used in the LBC chamber. We have found Hornady factory Grendel ammuntion with the 123's shoots exceptional well in the LBC chamber.
If you have ANY questions or issues please feel free to contact me via PM and I will work to clear up any if the misconceptions and wives tales floating about the Internet regarding the similarities and dissimilarities on the Grendel and LBC.
The best firearm for self defense? Any loaded one will do.