I shutter to think of all the things that could go wrong cutting dovetails with a drill press. Disaster is inevitable. Slipage of the bit in the chuck, lack of precise indexing, slop in the table piviting around that rear pipe shaft. And all of this on a barrel you worked so hard to make "just right". Fact is, it will take you just as long to set up the machine and index the barrel, for each cut, as it would to cut the dovetails by hand.
Two cuts with a hacksaw, a half dozen licks with the edge of my big horseshoe rasp and cleanup on the corners with a triangle file with a safe side, final fitting with swiss files. It's over about that quick. I don't hate dovetails nearly as much as I hate drilling a touch hole. Guess I've messed up more touch holes that dovetails.