I believe that's another typo, the 45/410 barrel is 24" long I think, but I'm not positive of that, it has a rifled barrel and a removable choke tube. It also has about 2" of free bore for 45 Colt since it has to be able to chamber .410 shotshells, and has only a bead front sight and isn't drilled and tapped for a scope rail.
A better choice would be the 45LC barrel down in the Handi section of the accessory barrels, it's a 20" rifled barrel, not 22" like it says, has sights and is drilled and tapped. It would be good for rechambering to Casull.
Tim