Big Bore Boom-Boom
I have since been educated by reloaders, (of which I am not one), that the .45-70 can be loaded to similar and higher specs as the .450 Marlin. This is great if you reload - not so great if you don't. Looking at factory specs for similar offerings in .45-70 and 450 Marlin, it's plain to see that the .450 Marlin is a more powerful cartridge. I have had zero problems obtaining ammo and if I were to reload, factory brass is readily available.
So, the bottom line becomes what you want the rifle for. If you're looking at buying a very, very powerful lever gun - it will be hard to beat the 450 Marlin. I have one and can tell you first hand that this gun with factory loads, eclipses the 45-70 using factory fodder. I shot my buddies 45-70 in order to take a break from the 450 - if that tells you anything. With cup pressures dancing around 50,000 pounds, this gun pumps out a bullet with stunning power. Hit differences between the two cartridges were obvious - even to the non expert. The 450 shoots flatter longer and harder. If you're not reloading and wanting heap big boom-boom - the 450 is the one. Ammo is pricey but like I said - available.
It's also a handfull - recreational shooting is punishing. I'm a big guy, (6'4" 260lbs) - I'm no slouch and no stranger to recoil and this gun gave me a run for my money. It was bone stock, so perhaps a recoil pad and a larger lever would help. Suffice it to say that tearing the skin off my knuckles on several occasions, was enough to convince me that Marlin needs a redesign on the lever itself. This despite many attempts to reposition my grip.
However, it's one of my favorite guns - bloody knuckles and all. The sheer power of this gun is something to behold. The looks from the unknowing on the range who think you're shooting a pistol caliber laver gun, when the 450 unleashes is something else...
Jaws drop as giant chunks of the 50-yard berm fly into the air.... I love it....