According to Greener in 1881, the British Proof Facilities would do a water pressure test of sorts on their tubes. First they would place a lead plug in the muzzle. Then pour boiling water into the breech followed by a lead plug being driven in from breech. Then they searched for leaks.
After the powder test, >>Common Barrels<< were untouched for a period of 24 hours to see if the >>Acid<< from the burnt powder ate its way thru somewhere. I am not sure exactly what they did w/ >>Uncommon Barrels<<??
Hochachtungsvoll,
Raimey
rse
