Using a Sinclair chamber length gauge, I measured chamber length to be 2.577”
SAAMI max cartridge lengths:
7 WBY - 2.549”
7 STW - 2.850”
I don’t think wrong reamer was used; rather went .028” too far with the 7 Wby reamer. Visual inspection of the chamber looks like a Weatherby shoulder.
28 thousands would match the 7 layers of painters tape on case head base; that seems too much to just blow out shoulder.
I’m thinking 7 STW using shoulder headspace would work as well as 28 Nosler and 7 RUM.
Nosler and RUM brass may be easier to find