I finally bit the bullet and cut my barrel to 16 1/2" with an 11 degree crown on it. I brought it almost out to the edge but left a flat to protect the bore.
The stainless for whatever reasons does not cut as easy as a regular steel barrel. It never cut any metal strings. It was all tiny bits or chips.
The barrel mic's at .620 so I can't just thread it for any 7.62 brake apparently. I don't really want to have to cut down the end of the barrel to 1/2 inch. I don't have a lathe for that.
If it shoots ok the way it is it will stay that way I guess.