I expect a mass produced barrel will have the chamber and leade cut in one pass with a reamer ground to shape.
The SAAMI specification is for a 2 deg 35 min taper from the chamber mouth into the rifling with no cylindrical throat as commonly seen in rifle chambers.
A chamber without that tapered leade is incomplete and incorrect.
You can accomodate it by seating all the bearing surface down in the case but might see leading or coppering as the bullet slams into the abrupt start of the rifling.
A real accurizing gunsmith will cut the leade and maybe even a throat* separately, either to suit the customer's ammo, or he will recommend ammunition.
*"Throating" a 1911 has come to mean grinding on the other end of the chamber for the purpose of feeding odd bullet shapes. Those old time accurizing gunsmiths would refer to that as "ramping" because they were "throating" the front of the chamber for a good entry into the rifling.
I have a few facts and a lot of opinions.
Last edited by Jim Watson; 01-13-2013 at 10:35..