[Bear_Slayer]

A gunsmith in Arizona was building muzzleloaders made from shot out 20mm Vulcan cannon barrels He cut out the part with the chamber throat erosion and had four feet of good barrel to work with. I suppose you could fins some surplus 25mm barrels from the Bradley fighting vehicles and do the same.

What would be the advantage to this, over buying stock and milling it down; other than possible cost prohibition. Even then, It's not that expensive.

[Vinnie_Vidi_Vici]

I think it would be much cheaper to go with the surplus barrels. How many gunsmiths could drill and rifle a 25mm bore, not many, and if they did it would cost an arm and a leg.