I spent all last Thursday at the Birmingham Proof House for a series of articles I'll be working on. I spent some time going through the steps of the proofing process with the proof master and his superintendent, and also got a look at their ballistics lab.

That does not mean I am able to offer real answers to problems of proof reported here, or their cause, which seem to be mostly coming out of London.

I understand that in the past the London house may have obtained at least some of its proof loads from various sources, so in theory some could have been too weak, thus allowing guns that might have failed to otherwise pass, and conversely some could have potentially been too strong, thus wrecking sound guns. Today the Birmingham house is supplying the proof loads to both houses.

I can report a few impressions: Birmingham was just accredited to ISO standards in late 2010, which means they are working to very strict international standards of control. I had a look at the lab, where shotgun proof ammunition was being loaded as I observed (this wasn't done for my benefit, I just arrived in mid-process). Proof loads are made in small batches, with each load's shot and powder charge individually weighed and, if necessary, corrected with additions or subtractions of powder & shot to meet the load's specifications. Batches are given lot numbers and are kept in temperature-controlled conditions, both for storage and just prior to proof firing. There has been lots of modern ballistics measuring equipment added since my last visit a decade ago. This is not a seat-of-the-pants operation.

Since 2006 two proof loads are fired per barrel, which is done to meet CIP standards. One could surmise that in some cases two loads are too much for some old guns but I do not offer the professional expertise of a ballistician.

My overall impression is that the Birmingham house is working, as I said, to very strict standards and is staffed by a team of experienced, conscientious technicians. I realize that this is not a full and satisfactory answer to many questions raised here but I do not think negligence is the root of reported problems.

I'll have more on CIP proof and the process of proof in coming issues of SSM.