It all depends on the load your using, the recoil pad, whether the rifle has a straight or pistol grip stock and the shooters technique. The Marlin .450 on the 1895 platform is capable of digesting powerful loads and is probably a stronger action then the 45-70 version as it does not have as much metal removed to accommodate the larger 45-70 rim.
I have been shooting peep sighted pistol gripped stocks with heavy loaded Marlin 45-70's since about 1990. I picked up my 3rd one about 15 years ago and did some work to it. The 26" Octagon barrel was cut to 21" and a Skinner "Alaskan" peep with a XS front flat post with the white lineup front. I had it Mag na Ported three years ago to assist with keeping the muzzle jump down for a faster repeat shot. Almost all of my shooting is done off hand or with the aid of shooting sticks. If I was putting a new load together I would dust off my dreaded Caldwell Lead Sled for the bench shooting.
The 45-70 is un pleasant shooting off of the bench for me and I assume the .450 Marlin would be the same. I carry my 45-70 in the off season for bear protection and hunt with other rifles. For over 25 years my load has been WW cases, H322 powder, WLR primers with a heavy jacketed bonded 405 grain Kodiak bullet from Alaska Bullet Works. When these bullets are gone I will switch to Starline Brass and the 350 grain Kodiak bullet. Recoil was some how easier to ignore before I got to be a senior citizen!
