Ammo Brief: 9mm Major – Gun Digest

Ammo Brief: 9mm Major

A quick look at 9mm Major, the slightly bigger older brother of the 9mm Luger.

There are good arguments to be made whether the 9mm Major is simply a hot 9mm Luger load … or another distinct chambering shooting 9mm bullets. It’s not a wildcat nor proprietary load; it has a distinct OAL measurement that makes it suitable for some guns and non-functional for others.

Moreover, some ammo makers have special packaging for the 9 Major loads, and it’s dangerous to shoot 9mm Major in many typical handguns chambered for 9mm Luger rounds, so it deserves some clarification.

Typical 9mm Luger ammunition is loaded to SAAMI specs of about 32,000-psi chamber pressure, which corresponds to velocities between 850 and 1,200 fps, depending on the projectile’s weight. In turn, 9mm Major ammunition is loaded to reach a Power Factor of 165 in IPSC or USPSA competitions. Power factor is determined by bullet weight times velocity, divided by 1,000.

To reach major power factor in USPSA Open Division competition, a 115-grain bullet must reach 1,435 fps, a 124-grain bullet must reach 1,331 fps, and a 147-grain bullet must reach 1,123 fps. If you look at the 9mm Luger loads and ballistics nearby, 9 Major loads are about 200-fps faster by bullet weight.

Note that 9mm Major ammunition is dangerous to fire in a pistol not designed for the excessive pressure generated by loading to the velocities needed. Many handgun makers caution against the use of +P and +P+ ammunition, and 9mm Major loads can generate pressures above +P+, making them unsafe for most off-the-shelf pistols.

Typically, only competition handguns are designed to accommodate these excessive pressures. The most essential feature in Open guns is a ramped barrel providing full case head support. Non-ramped barrels, or any barrel with a large cutout for the feed ramp, are not safe for 9mm Major ammunition.

*OAL: 1.165 ± .005

General Comments

There’s no prescribed pressure limit for 9mm Major as a wildcat round. Gunpowder selection is crucial when handloading. Only medium- to slow-burning-rate pistol powders are used because they produce lower peak chamber pressures when pushing the bullet to the same velocity as faster-burning powders. On its 9mm Major listing, Atlanta Arms notes, “**Warning: This ammunition EXCEEDS SAAMI Specification and should only be used through a competition race gun.”

Most 9mm Major rounds are loaded as long as possible to help keep peak pressure low. The SAAMI maximum overall length for the 9mm Luger cartridge of 1.169 inches. Black Dot Ammunition (Crawford, Alabama) notes that it loads its 9 Major rounds to 1.160 inches overall, which means the ammunition “will not chamber in most standard 9mm guns to prevent accidentally firing from any non-open type firearms.”

Other ammunition manufacturers load 9 Major, including JJR Ammo, C&S Ammo, Everglades Ammo, Vantage Reloading and Universal Ammo.

Editor’s Note: This article is an excerpt of Gun Digest’s Cartridge’s Of The World.

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