There is a way to do it. I did a brass pistol barrel, but made up a support fixture on my workbench. The drill ground like a boring bit and a support "sleeve/bearing was installed and supported it about 1/2 to 3/4 in behind the bit face, and along the shaft as well. I cleared the chips constantly, and used a brace. All by hand, it took me many hours to do it, but it worked. Not something I'd want to do again, but it was fun to try it. From a practical stand point, unless you want the experience of forging a barrel, I'd just buy them. The barrels available today are a bargain.