Whether 444 or 9.3x74 brass will work depends on your chamber. I believe the end of the 410 chamber is supposed to be about .454". If that is the case, you have .0015 left for brass clearance when it has a .451 bullet. Not going to work...
As you shorten the brass, the chamber gets a little larger. If it was intended to chamber a 45 Colt, then obviously there will be enough room for brass and a .451 bullet in the chamber with 45 Colt length brass. But if the chamber is reamed enough to take a 444 Marlin with a .451 bullet, then that chamber will also take a .454 Casull or a 460 S&W. Either of those are probably going to blow up the gun. A liabilitity conscious manufacturer wouldn't do that.
Take a peek at your chamber. Do you see a ridge where the end of 45 Colt brass would be? If so, you're not going to be putting 45 caliber bullets any deeper than that.
As you shorten the brass, the chamber gets a little larger. If it was intended to chamber a 45 Colt, then obviously there will be enough room for brass and a .451 bullet in the chamber with 45 Colt length brass. But if the chamber is reamed enough to take a 444 Marlin with a .451 bullet, then that chamber will also take a .454 Casull or a 460 S&W. Either of those are probably going to blow up the gun. A liabilitity conscious manufacturer wouldn't do that.
Take a peek at your chamber. Do you see a ridge where the end of 45 Colt brass would be? If so, you're not going to be putting 45 caliber bullets any deeper than that.