Bzzt!
Capt Quahog, you have the model number of that .45-70 wrong.
It's the
1895, which has some fairly important differences from the
1894, mainly a much longer lever throw necessitated by the rifle length cartridges in which it's chambered, and the bolt is round instead of square.
I can tell you that, just as with the 1894, the 1895 can withstand loads considerably more powerful than standard SAAMI spec factory loads of .45-70.
The reason that SAAMI spec .45-70 is so relatively mild, just as with SAAMI spec .45 Colt, is out of deference to all the old guns guns originally designed to fire blackpowder cartridges (Colt SAA and clones for .45 Colt handguns and Springfield 1873 "Trapdoor" for .45-70 rifles) that would be wrecked by loads at the full potential of the respective cartridges.
Loading data for .45 Colt is in two categories: SAAMI spec and "Ruger/TC
only" for loads that exploit the full potential of the .45 Colt case.
SAAMI spec .45 Colt loads are limited to an anemic 14K PSI, while the cartridge is stoked all the way up to 30K PSI for more capable guns.
Modern metallurgy, beefier frames, and heat treating allow these .45 Colt handguns to withstand "full potential" .45 Colt loads: Ruger Blackhawk, Blackhawk Bisley, old model Vaquero (but NOT the new Vaquero!), Colt Anaconda, Ruger Redhawk, Dan Wesson, Freedom Arms, and Thompson/Center Contender.
With rifles, the Winchester 1892 (and its clones, including the Rossi version), Winchester 1894 and Marlin 1894 can all handle the same "full potential" .45 Colt loads as the above mentioned handguns.
The story of load capability for the .45-70 is a bit more complicated, since loading data is actually in
three categories.
SAAMI spec loads to be used in the Springfield 1873 "Trapdoor," Sharps, rolling blocks, and all replicas are at the lowest level SAAMI spec maximum of 28K PSI.
Moving up in pressure, is your Marlin 1895, Winchester 1886, and 1886 replicas, all of which are capable of handling loads up to a maximum of 40K PSI.
Finally, the strongest rifles include the Ruger No. 1 and No. 3, Winchester/Browning 1885 "High Wall," and the Siamese bolt actions, all of which can handle an impressive 50K PSI.
Naturally, it's perfectly safe to use SAAMI spec .45 Colt and .45-70 in all guns so chambered, but extreme caution must be exercised to ensure that anything loaded beyond that is fired exclusively in guns at least strong enough to safely withstand them.
Doing otherwise will wreck a valuable antique at the best and cause serious bodily harm or a call to the undertaker at the worst.
You have been warned.