Sir Larry,
Might take two TakeDown rifles, a long action and a short action
Find a .300 WinMag BLR TakeDown
and see if the .450 Marlin Barrel could be transplanted ?
Then is there enough meat in the .450 Marlin barrel to lengthen chamber by 1/2" ?

If not, re-throating the .450 Marlin would certainly be a worthy project.

Ron aka "Rip" for Riflecrank Internationale Permanente
NRA Life Benefactor and Beneficiary
.458 Winchester Magnum, Magnanimous in Victory
THE WALKING DEAD does so remind me of Democrap voters. Donkeypox.