![]() It’s common for a cartridge to be held to a Maximum Average Pressure (MAP) limit, which is the average of the maximum pressures measured for a set of test cartridges. Importantly, the way that pressure standards are created is very important. In Europe, Megapascals (MPa) is common, as well as occasionally bars or atmospheres. The pressure of firearms ammunition can be measured in several units: Most commonly used in the United States is pounds per square inch (PSI), but the older copper units of pressure (CUP) is still in use as well. Over the course of the pressure curve, several notable highlights occur: These include the maximum pressure, which is the highest pressure level on the curve, the uncorking pressure, which is the pressure as the bullet is leaving contact with the rifling, and – in the case of weapons with gas systems – the gas port pressure, which is the pressure as gas enters the gas port. ![]() Over the course of the firing cycle, pressure in a firearm will increase rapidly and then decrease more gradually, and the graph of this change in pressure for a specific load of ammunition is called its pressure curve. These subjects will come up again when we cover bolt thrust and swept volume, later. In both cases, the pressure acts upon an area, and therefore the force against either the case head or the bullet is proportional to the area of the maximum internal diameter of the case and the bullet base, respectively. Likewise, the pressure also pushes backward, against the case head and the breech face. Some of this pressure acts upon the base of the bullet, pushing it forward. ![]() Just like inside a balloon, or in a champagne bottle, pressure is exerted in all directions after the ignition of a cartridge. When a gun fires, a similar effect is at work. ![]() Ballistics 101: What is caliber, exactly? ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |