A slight expansion to VA Bigbore's excellent summary:

1) Bill Alexander says that the Grendel was designed as a deer cartridge for the AR platform.
2) The cartridge does very well in this role.
3) While the 6.8 and Grendel are similar in performance at short ranges, the 6.5 bullets tend to outperform the .277 bullets beyond 250-300 yards.
4) SAAMI has approved specs for the Grendel and the Grendel trademark has been released.
5) We should see an increased number of offerings towards the end of this year (takes time to do these things!).

What is a blot gun?