I've got to agree with Boats, SKB, Joe Wood and Shotgunlovers comments.
My thought is that you have a very special gun there, rather uncommonly choked. The EJ Churchill XXV, was a very specifically crafted gun, capable of amazing game performance if used in a specific intuitive shooting style (get one of Robert Curchills books!). It was copied by many, and virtually all of the copies missed the mark of such a dynamic gun. Unfortunately many people have shot these "Churchill" clones, and been disappointed. Few who have shot a real XXV, particularly from the golden inter-war years, have anything but high praise for them.
Get out and shoot it, shoot it a lot, and see what it can do. I think you may well be very pleased with it as it is.
Mine (12 bore, 2 3/4", 1931 SLE "Field" XXV) shoots very nicely with the Gamebore Pure Gold 2 1/2" paper case, fibre wad loads that I use.
Good shooting!
