https://www.forgottenweapons.com/mosin-nagant-factory-pressure-test-rifle/ http://www.patreon.com/ForgottenWeapons Cool Forgotten Weapons merch! http://shop.bbtv.com/collections/forgotten-weapons How did people determine chamber pressure in the years before computers and fancy electronics? Well, by squishing a calibrated slug of copper. Factories would convert rifles specifically for pressure testing use by adding a pressure ring around the chamber, drilling a hole in it, and then threading in a gage to crush a block of copper. This Mosin Nagant is an excellent example of the system, complete with the all the testing apparatus! Contact: Forgotten Weapons PO Box 87647 Tucson, AZ 85754