set your mind ar ease, all modern barrels can be filled to the top, double balled, and fired. There are pics over at Dixie to prove it.
Not suggested you do so.
WHen asking about barrels, there are so many types. Per firearm style.
Long, short, octigon, round, swamped, and many more.
You need to know which type of rifle you are going to build.
The best parts can be found at Jim Chambers flintlock.com
or Muzzleloader supply. com
Chambers makes the best all around kits. The gals at MLS can muster up a better section of locks, stocks, and barrel.