Barrel Index, Need Help

[Bruce_in_Oz]

They didn't use index marks because they used a VERY nifty machine to wind in and torque up the barrel to its correct location.

This machine used a "split collet" sort of arrangement. If you have ever wondered about the "odd" profile of the rear end of the barrel, wonder no more. The "step" on either side fits the clamp shells, which, in turn are attached to a drive mechanism actuated by a longish lever.

Part of the trick is to select a barrel that pulls up by hand to a position "X" degrees short of final, torqued-up alignment.

When I find the appropriate instruction here, I'll post it verbatim.