How about an H&R Handi-Rifle in .445 Su
The problem is the twist in the nef. A 1/38 might get a 270 gr stable,but it woun,t go heaver. You will need a faster twist. Marlin was asked why it ,s 444 marlin was rifled 1/38 and not 1/20 like 45/70. They did not know must be an old standerd for the bp rounds. The new marlins have a faster twist.Hand loader big boar rifles has a art on the 444marlin on a roling block. I have a danWesson in445 supermag.. The 240 gr. is to light for hunting deer or large game at the 445 vol. Reloading manuals keep the presures at the same as 44 mag. Maybe that marlin ownes nef they will change the twist and chamber it in 444m.If it,s the new browning (jap) it will handel the 444m or 445s It was chambered in 454 casul and 243 on a low wall. So that would not be a problem. But what is the twist on the browning? Most of the time you set the barrel back then rechamber to clean out the old chamber. Make sure that whoever rechamber know,s what he is doing or you might have a junk nef barrel. It cant be set back like a screwed on barrel.