The 444 SAAMI chamber, as used by Marlin, has a very short throat, and some 44 magnum bullets with full diameter front bands may not chamber.
Here's a couple of suggested nose designs. They will result in an overall cartridge length of 2.565" if your cases are 2.55" long.
A bore rider. The ideal diameter of the bore riding section is debateable and will in any event depend on as-cast tolerances.
A reduced diameter nose.