Barrels made by the United States Government, or barrels made for the Government, are subject to severe proofs. At the armory at Springfield, the barrels submitted for proof are loaded, first, with a 500-grain slug and 280 grains of powder, and afterward with a slug of the same weight and 250 grains of powder. An inspection of the barrel is made after each firing, and other inspections after rifling, browning, etc.
Probably the most severe proof of barrels was made with the Turkish Peabody-Martini rifles as made for the Turkish Government by the Providence Tool Co. The barrels were first proved for strength, and were loaded with 205 grains of powder and 715 grains of lead. The regular cartridge for service contains only 85 grains of powder and 480 grains of lead.
Figure 26.
Proof Marks on Gun Barrels.—The marks applicable to the definitive proof are the proof and view marks of the two English companies, viz.: the London and the Birmingham. The provisional proof marks consist of, for the London company, the letters G. P., interlaced in a cypher surmounted by a lion rampant, and for the Birmingham company the letters B. P., interlaced in a cypher surmounted by a crown. The London marks are shown in [Fig. 26], and the Birmingham in [Fig. 27].
The method of affixing the proof marks in arms of the first and third classes, the definitive proof mark and view mark is impressed at the breech end of the barrel, and, if the barrel be designed for a patent breech, the view mark is also impressed upon the breech. In arms of the second, fourth and fifth classes, the proof mark is impressed at the breech end of the barrel; the definitive proof and view marks are impressed upon the barrel above the provisional proof marks. If the barrel be made with patent breech or with revolving cylinders or chambers, the view mark is impressed upon the breech or upon the cylinders or chambers, as the case may be.
Figure 27.
On all barrels the gauge size of the barrel is struck both at the provisional and at the definitive proof. These gauge marks are readily recognized, as shown in the cuts of the proof marks.
Barrels stamped with London marks are not always made in London, for some gunmakers send their barrels to London to be proved, because guns so marked find a readier sale. Barrels with foreign proof marks are exempted, except in case of being marked as of English manufacture. Old muzzle-loaders, if of English manufacture, intended for conversion into other styles of guns, must be subjected to both provisional and definitive proof.