Thank you for the photograph. It was built and proved as a 16 bore.
The date stamp (KXB) is for 1959.
It has clearly been chamber sleeved. If that had been done in the UK it should have gone back to the Proof House for re-proof.
See page 156 of Diggory Hadoke’s book “Hammer Guns” for a photo of the Proof Marks on a 16 bore chamber sleeved to 20 showing the 16 bore dimensions but the 20 (in a diamond) chamber marking.
At pages 156 to 158 he discusses the process, and remarks that “counter intuitively” it seems to work better than might be expected.
You might find yours works well, but you need to consider how much you have invested and the problems you could encounter on trying to re-sell it. I see it was described to you as a 2 3/4” 20 bore. Did you buy it from a dealer, at auction or privately?
Last edited by Parabola; 05/12/22 03:34 PM.
