My thoughts are that the origional owner of the gun wanted an extra factor of safety in their 2 1/2 chambered guns. To achieve this objective, they specified that their 2 1/2 chambered guns be subjected to the 2 3/4 proof test.
Another possibility is; for example, in the case of Webley and Scott, they may have used their 2 1/2 guns guns ability to pass the 2 3/4 proof test, as a sales incentive. I think the risk decribe by Burrard was likely due to individuals owning a used gun, after seeing the 1 1/4 oz proof mark on the action; purchasing 2 3/4 cartridges with 1 1/4 oz loads! Just another case of lack of understanding and human error, that could result in a serious accident.Your question related to current test proceedures should be directed to the Birmingham Proof Master, Mr, Roger Hancox.
By the way, Vic Venters, published an excellent article on the. "Rules of proof", in the Jan /Feb 2009 edition of Shooting Sportsman.
