I don`t even know if GM offers round botton rifling? I know Rice does, not sure about DeHass?
Just so it's clear, I wasn't lobbying for round bottom grooves...is just that it happened to already be made up laying on a shelf in the configuration I needed...38" D-weight, swamped, .58cal, etc...and they were out of what I needed in square groove.
I will say that I've noticed the following differences compared to the .58cal GM square bottom barrel I had:
1) The .016" round bottom groove Rice barrel seems to wipe completely clean with a single cleaning patch:
2) The deeper rounded groove design makes the bore feel noticably larger;
3) The same .570" x .018" pillow ticking PRB which was a tight fit in my .58cal GM square groove slides down / seats noticably easier in the round bottom grooves;
4) Sighted it in for deer season with Oxyoke .022" precut/prelubed patches;
5) Seems the bore was polished / finished better than any T/C or GM barrel I've had;
6) Far greater accuracy capability than I'll ever have;
So what started out as an "OK, I'll try that one" kind of a purchase, given all the above I wouldn't trade it for anything.