If I really wanted to remove a shrouded barrel like used by the model 69 I would not use a tool that engaged the rifling. First it would be difficult to make and second it would be hard on the rifling. I think there is a better way to do this.

First get or machine a piece of brass square stock that would fit down the barrel. I would also get some low temp solder that melted below 200f. They make this type solder for various uses usually using some type of tin, lead, bismuth, indium alloy. Plug the forcing cone, mount the in a padded vise by the grip frame with the cylinder removed so the barrel is pointed up. Use a frame wrench made to fit around the yoke cut like a normal frame wrench. Then heat the solder, barrel and the brass square stock to about 250-300f. Pour the barrel 1/2 way full of solder and stick in the bar. Let it cool and unscrew the barrel using a wrench on the end of the brass bar and holding onto the frame wrench. Do whatever, then reinstall.

Remove solder by warming up the gun and scrubbing the bore. With no flux it isn't going to bond to the stainless well in the first place. Only function is to make a perfect mate of the barrel to the brass bar.

Machinist sometimes use this type of solder to mount small odd shaped pieces to something they can chuck up or put in a machinist vise. Do a net search for it, lots available.

Someday I am going to get some that melts around 135f and cast a spoon out of it and then give it to someone to stir sugar in their coffee. LOL