I'm too stupid to post pic's but you can get a very eye pleasing contour by tapering from the middle step to the foot of the chamber step, and then, instead of the American convex bulge chamber transition, turn a nicely radiused concave transition. I have done 4 or 5 like that and gotten some compliments. Move your steady rest very often keeping it close to the tool (HSS), use plenty of oil, I use a gravity dripper, mind the tension betwixt your centers, as it warms. I turn 'em slow and cool. I've only had one bbl bend a tad, which I easily straightened. It's very good steel.
one man's opinion.
