Green Mountain barrel

[JIMHAY97]

I've been thinking that I'd like to make a bench rest slug gun. Green Mountain sells a 40 cal barrel blank, BX4016-2, 1-16 twist, 1.4" dia and 35" long. They say it's for a cartridge gun but I was wondering if it couldn't be drilled and tapped for a breech plug and used as a muzzle loader. I'm a retired machinist and have access to machines to do the work. Anybody have an opinion on using this barrel? Any other barrels I should look at? I know this is kind of a vauge question but I don't know enough yet to ask detailed ones.