Fred Bowden has a whole series of fixtures....I use a 3/4" pipe clamp that I modified the jaws to have brass pins sticking out to hold the barrel in place.....adjustable for any length of barrel...good for ejector rod housing an cylinders too...
I have an article in the next Engraver magazine showing a new pistol barrel fixture and a new one for the recoil shield. Both are designed for Colt Single Action Army style pistols, but the barrel fixture can be used for other barrels between 4 3/4 and 7 1/2", .38-.45 caliber. It is compact and solid. I have been cutting a 7 1/2" SAA barrel and it works great. The article describes the fixtures and how they work and I ask for input from the readers based on this information. I will decide whether to manufacture them depending on the responses.
Search under barrel holding. There is several pictures of the barrel holder I made from a carpenters clamp. You can make some cones out of brass or do it like Marty Rabeno made his with thermo loc.
Sandy.
P.S. I would post the link to the thread but I haven't figured out how to copy and post from my IPad. Sorry.