The 444 Marlin is literally a 44 Rem Mag lengthened by .940", or 30 grains of capacity (Ackley in vol 2 refers to 444 as shortened 30-06, with a rim and necked up to .429") Because handgun bullets tend to have lesser sectional densities and such lower ballistic coefficients, and the 444 is nominally used to shoot handgun bullets, the 444 is a short to medium distance hunting cartridge - beyond 200 yards bullet drop becomes unacceptable. Also because .429" handgun bullets are designed to expand and operate in the 800-1400 fps range, when one hits the target at greater than 2000 fps, they tend to overexpand and fragment, generating huge surface wounds, and little penetration. The use of nonexpanding bullets resolves this problem. Maximum operating pressure is 44000 CUP or 42000 psi, respectively 4000 CUP and 6000 psi above the 44Rem Mag.