The .444 Marlin Ammo is a rifle cartridge developed in 1964 by Marlin Firearms and Remington Arms. It was designed to fill the gap left by the absence of the .45-70 cartridge in new lever-action rifles at the time. The .444 Marlin ammo became the largest lever-action cartridge available and is primarily used in the Marlin 444 lever-action rifle.

This cartridge resembles a lengthened .44 Magnum and offers a significant increase in velocity. It is capable of pushing a 240-grain bullet at velocities over 2,400 ft/s, generating 3,070 ft⋅lbf of energy. SAAMI rates this cartridge at 44,000 CUP (Copper Units of Pressure). The .444 Marlin ammo functions efficiently when used with cast lead bullets, allowing shooters to optimize the alloy for strength and expansion at higher velocities.

To achieve the best cast bullet accuracy in the .444 Marlin ammo, bullets sized to .432″ diameter are recommended, regardless of whether the rifle has the older “Micro-Grooved” or newer “Ballard” style barrels. The bullet diameter is primarily dictated by the large diameter of the chamber throats rather than the groove diameter of the barrel. Ensuring a closely fitting projectile greatly enhances the cast bullet performance of this cartridge.

Various commercial molds are available for hand-casters, including the SAEC #433 mold that casts a 300-grain gas-checked bullet and the Lyman 429640 at 280 grains. Proper cartridge length is maintained by seating the bullet to the correct depth and using a crimp die to provide a firm crimp, preventing slippage in the magazine tube.

Since its introduction, Hornady has developed specialized ammunition for the .444 Marlin, including a heavier 265-grain .430″ bullet designed specifically for this cartridge. They also offer a 265-grain interlock “Light Magnum” that boosts velocity and energy. Hornady’s LEVERevolution ammunition features a soft polymer spire point, allowing safe use in tubular magazines and offering increased velocity and energy at various distances.

Other companies such as Buffalo Bore, Cor-Bon, Underwood Ammo, and Grizzly Cartridge offer loadings for the .444 Marlin in bullet weights up to 335 grains, providing a range of options for different shooting preferences and purposes.