anybody done it. how did it turn out for you.
I have turned similar profiles by offsetting a tail stock, but not a barrel
I wouldnt suggest it if you want to maintain the same degree of accuracy you have. When you remove material on the outside of a barrel the inside may very well change depending on how the barrel was constructed.
It is a tough job and a real PIA. I was trying to duplicate a existing rifle barrel contour from a straight blank on a regular lathe. The original had two different tapers and a smooth convex/concave transistion between them; in other words, a basic light-weight sporter barrel.
I tried off setting the tailstock to do the longest straight taper, which about 2/3 of the barrel. A follow rest doesn't help and a steady rest gets in the way. I ground the lathe bit to have zero side rake and no point radius to minimize the barrel deflection and went to work. Could only take very light cuts as heavier ones caused too much chatter.
The balance of the barrel, I duplicated by using the cut-off tool to cut grooves to depth and position to match the original contour. My grooves were about 1/2" apart along the barrel. A follow rest helps here. I then turned off the metal between the grooves until the depth matched the shallowest groove. That left the barrel roughly outlined by a series of straight, stepped rings. The smooth outline was finally achieved by filing the steps off while running the lathe at high speed, a very slow, tiring job.
Chatter was a constant problem and it is easy to cut too deep. I don't recommend my approach, it is simply to much work.
think button rifled barrels may open up a tad if muzzle turned down ...on match barrels we used to leave a larger diameter at muzzle end for an inch or so.....for smoothing , abt 45 yrs ago , built a 1x42 band sander out of two pieces angle, 3 caster wheels& ,spring loaded idler arm from flat stock, & a 1/3 hpmotor ...it mounts on lathe tool post & travels down the barrel ..i was VERY happy to lay down the draw file /emery cloth ( ever clean up an O3A3barrel?) ...also made a stand so i can mount it on bench & use it for other work .....
Don't forget to cover the ways when using abrasives on a lathe.
There is a description in one of Brownells Gunsmiths Kinks that is worth noting to help with the chatter. It uses a Four sided tool post to hold the cutting tool on the left hand side and a brass rub on the right hand side. You have to machine the width of the toolpost before setting the rub bar in contact with the work.
I recontoured a few 2 groove Springfield barrels for various guns some years ago. Most turned out pretty well. Used a steady rest to support the center of the barrel and turned the taper in short sections. I used tail stock set-over for the tapers. As I remember, one barrel had to be straightened after turning. These were good shooting lead bullet barrels.