Handloader1, with all due respect, you are only 1/2 right-yes, to considerably beat the .450M with a .45-70, you need a strong action-they can give an advantage of about 500fps in some cases-did in my Ruger No.1 vs. my 1895M, but it has been my experience that the .45-70 can match the .450 (if not surpass it) in the 1895's, my 1895 was faster than my 1895M for some reason, although the difference was small, usually an advantage of 200fps or so in the .45-70 with identical loadings (powder charge and bullet).

Marlin themselves claim that the .450M is belted so that it cannot be chambered in a .45-70 that isn't designed for high pressures, the chambers are virutally identical save the belt, the 1895M and 1895 are virtually the same gun, there is no reason that the 1895 can't handle the same pressure that the 1895M is able to...The belt is the ONLY true difference in the two guns, and it is FAR from enough to create any advantage in energy.

The 1895M I had never could touch 2000fps with any 350grn bullet I loaded, most were lucky to break 1750fps, while I've pushed a 350grn hardcast to 2077fps average in my .45-70 1895stainless.

And yes, the .450M is about at it's maximum abilities from the factory, leaving very little or no room for improvement on it's velocities.

As I said before, for a non-handloader, the .450M is the viable chioce, for the handloader, the .45-70 is the way to go.

In my rifles, the .45-70 was also inherently more accurate, every .45-70 I've owned has shot well with any bullet I've fed them, while I sent my first .450M back because it was so inaccurate, and my second was pretty finicky as far as what it would like to shoot.