I'm back in the shop , setting up the mill to drill and bore the breach block hole . reading the text, it says drill at 3*. So I'm thinking tan. of 3* = .0524.
.0524 x 2.5 (width of receiver) = .131" . If you measure the drawings figures 3-5, 3-7 and 3-8, you come up with roughly .05 total...