Ok, I've got a CMMG MK3 and I want to remove the barrel.  CMMG does not list barrel nut wrenches on their web site and my email conversations with Brian B. at CMMG tech support leave me wanting to go postal on someone.  So....there's got to be someone on this board who's removed the barrel nut on their MK3, whose barrel nut wrench did you purchase to remove the damn thing.  And no, a pipe wrench is not an option!

I don't know what the actual tool is and have never removed one but my mind went to a spanner wrench as well as a strap wrench.

I think it is the same as the DPMS .308 nut . Have you tried a DPMS wrench ?

Well with a little internet sleuthing it seems there may be 2 different barrel nut versions for the factory MK3 handguard. One looks like it uses a spanner wrench  with a pin, and the other a larger version of the RE castle nut tool. FWIW it doesn't look like either one would be removable with the factory DPMS LR-308 tool.

Have you removed the handguard from the barrel nut to look at the barrel nut yet? Posting a pic would allow us to help you further. Even if there isn't a "factory" barrel nut tool I am sure you will be able find something adequate to remove it.

And I sincerely doubt you will need to bust out the pipe wrench to get it off haha...

In case any one is interested.  A friend of mine had a box of various barrel nut wrenches.  After trying all of the wrenches, the Bravo Company KMR barrel nut wrench was the only one that fit the CMMG MK3 nut.