Nope, I'm not complaining about any barrel makers. I am very happy to be able to get such an assortment of sizes and shapes. When I started building muzzleloaders, all one could get were straight octagon bbls.
As Rich has said, that these barrels are made by humans, but it's YOUR responsibility to make sure it's right. Do not assume it's right. Assume your airplane/car is safe? No, you check it out, or get it checked out.
My advice based on my experience, from 'geeze, I wish I'd looked before I put all this time into the project' . Once cut into, a barrel is well nigh impossible to exchange.