Wheeler makes barrel nut wrench for the smooth nut. I used it to remove 2 smooth nuts no problem, and replaced them with the castellated ones after. I bought the 2 pack of savage barrel nut wrenches, one for each type of nut.

I think I got them from Opticsplanet but cant remember now. I know midway or brownells has them too. Both wrenches cost like $30 or less.

Go-no-go is a must and I agree you want a action vice and not a barrel vise. Somehow a vice around the receiver works better.

Altho I use a regular vice and made vice clamps out of wood for the action. drilled a 1.5" or 2" hole in a 2x4, then split in down the middle and put that around the action, then clamp it all in 6" vice. I've removed more than a dozen barrel nuts with it thus far with no problems.