Finally found it on Calhoon's website. It shows two models, one for rimmed cases like the Hornet, and up to the .223 based cases. It does not say if it will work with the 7.62x39 based cases like the Grendel though. I may give him a call tomorrow and see.
I have one of the Bobsled types for my Hornet and it works great, but hangs down a bit, although I could cut it off some. I did e mail CZ a question about one for the Grendel and they stated that the 7.62 model works.