Pedersoli Pedersoli
Black powder Magazine
Proofing the U.S. rifle muskets in the 1860s and today

So you actually do not know what the V and P letters stand for on the barrels of the U.S. rifle muskets? If not, this is the time to learn it from the 1862 U.S. Ordnance Manual.


These stamps are connected to the proofing process of the barrels. Pressure testing is not a modern idea, in fact even the smooth bore muskets of the U.S. Army and Navy were proof tested. The U.S. rifle musket was an effective, formidable, strong infantry arm, up to the highest European standards.


Before proofing the barrels with high pressure loads the rifle musket barrels had to pass 8 visual inspections during the production process. The inspector verified all the parameters with proper gauges in every significant stage of the production. In the final stage the barrels were ready to be assembled with the breech plug, but all inspections took place before installing the breech. If a barrel did not pass any of the 8 inspections it was condemned and marked with the letter “C”. If the defect did not prevent using parts of the barrel for shorter firearms, the letter “C” was placed only on the defective section.


If the barrel passed the visual inspections it was time to pressure test the rifled bores. For this purpose special proving breech plugs were used instead of the standard breech plugs. In fact only the bores were proofed, the assembled bores and the complete rifle musket was not.


The proofing started with installing the proofing-plug and loading the first proof load: 280 grains of the same musket powder used for the normal cartridges, an over powder wad, a 500 grain ball and an overshot wad. The charge was rammed with a copper loading rod. If the barrel did not burst, it was time for the second load of 250 grains of musket powder, wad, 500 grain ball and wad again. If the barrel remained intact, it received the inspection marks: “V for viewed, P for proved with the eagle's head under them, placed on the left square of the barrel, opposite the cone seat. The barrels will be immediately washed clean in hot water and dried after which they will be again carefully examined.”


The cleaned barrels were inspected again, and condemned is necessary. The bores were straightened again, and prepared for the final assembly.


Today the replica manufacturers have a more difficult task is they want to meet the high standards of CIP (Permanent International Commission) proofing. The CIP lays down common rules and regulations for the proof of weapons and their ammunition in order to ensure the mutual recognition of Proof Marks by its member states. Fourteen countries are CIP Member States.


Each and every blackpowder firearm must pass a pressure proof test in the official CIP proof house of Gardone to receive the modern blackpowder proof marks. The official modern proof loads for .58 caliber rifles are quite close in weight to the 19th century proof loads being 15 g (231,5 grain) of blackpowder and 39 g (601 grain) in bullet weight. But the powder used today is much hotter than the 19th century U.S. Government musket powder (the modern proofing powder is the Swiss No. 2. 3Fg powder which is finer and stronger) and the barrels are not proofed in proofing machines but in the fully assembled (but white finish stage) rifles. After firing the barrel, the breech and the stock are inspected for any kind of cracks and damages. Only the spotless rifles will receive the final proof marks and only these rifles qualify for shipping to the customers all over the World.


Balázs Németh


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