just wondering. whoever does make 'em, they do a helluva job! keep up the good work.

That's classified, I could tell you but then would have to kill you.....all.  

Just know that the .gov profile 1/7 twist M4 barrels do a lot of things well; one is kick ass.

I love the upper setup I purchased from CMMG in preparation for the end of the AWban.  Damn solid, accurate, and lighter than the HBAR variants I had used before.  They also have M4 feedramp cuts and are chrome lined.  Better than most of the gunshow barrel dealers and at a reasonable price!