Overpressure Ammunition - Custom and Handloaded Overpressure Cartridges

Custom and Handloaded Overpressure Cartridges

Some older cartridges, especially those that were originally blackpowder cartridges, such as the .45 Colt and .45-70 (both dating from 1873), are capable of being loaded to far higher levels than was originally possible. Because modern firearms are much stronger than the original black powder era firearms (for example, many .45 Colt guns are built on the same frame as .44 Magnum versions) a combination of modern firearm and specially loaded ammunition can provide performance to rival modern cartridges. However, these high-pressure loading can only be used in modern firearms. Because of the potential danger in shooting these "unofficial magnum" cartridges, they are generally only available if handloaded or purchased from low-volume specialty manufacturers. SAAMI specifications may or may not exist for these loads, so extra caution must be used. Generally, the manufacturer or data publisher will specify exactly which makes and/or models of firearm can or cannot be safely used with a given load, such as "Only for use in Ruger and Thompson/Center Contenders", "Use only in modern Marlin and Winchester repeating actions" or "Ruger No. 1 and No. 3".

In addition to the SAAMI recognized Ruger .45 Colt load, there are many other higher pressure specialized loads available. In many cases, these loads are not pressure tested, but are tested by firing in particular firearms, then checked for signs of excessive pressure. In some cases, high pressure ammunition is restricted to law enforcement sales, such as Federal's .38 Special and 9mm +P+ Hydra-Shok cartridges. The following table lists some non-SAAMI +P loads for which the manufacturer publishes pressure information.

Cartridge Standard pressure +P pressure Notes
.44 Magnum 36,000 43,500 21% increase, Garrett Cartridge, Ruger and Dan Wesson DA revolvers, long-frame single action conversions
.45 Colt 14,000 23,500 68% increase, Accurate Powder loading manual, Ruger and T/C only
.45-70 28,000 35,000 25% increase, Garrett Cartridge, modern rifles including lever and break actions
.45-70 28,000 40,000 43% increase, Accurate Powder loading manual, Ruger and similar high strength actions

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