I'll pm you about the brass.

The new brass is 3" .577 Bertram. It does not fit the chamber unsized. Full length resized in the 2-3/4" dies it just barely fits. The brass is a touch tight in the head area but can be finger pushed in the chamber. I will need to get a 3 inch set of dies.

I seated a bullet in the case and tried to chamber a round. Would not go in all the way. At first I thought it was because bullet shape was wrong or no throat. After some checking,it looks like the neck with bullet seated is to large. Thick case walls

I went gopher hunting today and shoot over 500 rounds (Gophers 57, DD 483) and I am to tired to mess with it tonight.