The Provisional Proof is just for the basic tube before any work is undertaken in order to show any flaws. This procedure is nor compulsory but advisable to save a lot of work being done to a faulty tube. Initially, when the 2" chamber guns started to make their appearance, the Proof House insisted in subjecting them to the same Definitive Proof as a 2 1/2" chamber gun and that is why some early 2" guns have the 1 1/8th. ounce mark on the barrel flats. Later a compromise was reached between the Gun Trade and the Proof Houses which resulted in a lower proof requirement for 2" guns.

I've been at the Proof House in Birmingham when Provisional Proof was taking place. If you have access to Greener's 'Gun & its Development' you will see the illustration and there is no change in how it is done other than the powder trail is ignited from an old car battery rather than a percussion gun lock and a piece of string running through a small hole in the wall. A series of bangs as the powder packed tubes go off in rapid succession and then the iron louvres are opened to let the smoke out. Once the 'all clear' goes all the barrel tubes are dug out of the sand beds. All very 'low tech' but it works! Lagopus.....