Rechamber .450 Marlin H&R Question

[Tim50]

I have a chance to pick up a .450 Marlin H&R from a fellow who realizes it is too much for him. I have no need for a .450 but I do have a .454 Ruger handgun. Can a .450 H&R be rechambered to 454? I have read that the pressure of a 454 is very high. I am not a gunsmith so please excuse my ignorance. Thanks for any advice.

[John Traveler]

If that H&R rifle you are talking about is th break-open single shot built on the old Model 158 "Topper" frame, the answer is NO.  You can't re-chamber to the .454 Casull because the .450 Marlin chamber is already larger in diameter than the .454 casull, which is same diameter as the .45 Colt.

In addition, the fatter belt of the .450 Marlin chamber would prevent rechambering to .45-70, .458 American, .458 Winchester, etc. because a standard belted cartrige would not headspace properly.  The .45-70 chamber would have that fat belt (UGH!) at a critical point near the cartridge head and be unsafe.

Short of being forced to handload more mild .450 Marlin ammunition, I dunno what you can do to make that gun shoot easier....

[John Traveler]

Sorry, I forgot one last thing:

Your idea of re-chambering to .454 Casull would not be feasible because the groove diameters are too different.  the .454 Casul is .452" while the .450 Marlin/.45-70, .458 Winchester are all .458".

If your barrel is removable (can be unscrewed), the chamber can be set back and them rechambered to those big rifle cartridges.

HTH
John

[gunnut69]

The H&R Handi Rifle is not a screwed on barrel.  This is a top break action and the barrel has it's own frame mount.  It may be possible though to buy a different barrel for a milder caliber.  A 22-250 or perhaps a 30-30 might be considered.  The 450 Marlin is not rechamberable to any current caliber..  Handloading may be your only recourse if you wish to keep the rifle.