I have not attempted any sort of a structural analysis on my BPCR M1885 High Wall. A rough and crude analysis would require measuring receiver wall thickness, (the thinnest part) and figuring out the load path through the dropping block. I think such an analysis a waste of time for my purposes as it is obvious by looking at the thing, these rifles are extremely strong.
Many of these historical actions are, when made of modern steels, extremely strong. While I think the Remington Rolling block an ingenious action, I do not think it a strong action as the load is carried through those action pins. And, the action has zero features to protect the shooter from gas release. I have looked at a number of early single shot action designs, and from memory, they all appear to be very strong. I can say the Martini-Henry is a very strong and safe action.
The problems with these early actions were the materials of the day. These things were made out of plain carbon steels which were extremely soft, then case hardened for a wear surface. Considering they used black powder, the materials were fine for those low pressure cartridges. I find it interesting to read, that if the chambers of black powder rifles are greasy or wet, when a black powder cartridge is fired, the case is pulled up into the throat of the rifle due to the strength of the bullet crimp. There is just not enough pressure to fix the case to the chamber walls due to the low pressures created by black powder combustion. Another issue with the materials of the day is their inconsistency. Vacuum tube technology started about 100 years ago and it did not instantaneously spread to manufacturing facilities. Springfield Armory produced 1,000,000 brittle M1903's, from 1903 and 1917, because Springfield Armory was not using temperature gages in the forge or heat treatment departments . Where heat was applied, the temperature was judged by eyeballs. The end result was that at least 1/3 of the receivers produced in this period were overheated and are so brittle that a sharp impact will cause them to shatter. The other 2/3 rds of receivers were so suspect, that an Army board recommended scrapping all of these receivers in 1927.
The steel manufacturer's of the day similarly lacked gages or process controls and therefore any metallurgical analysis I have read of historical steels indicate a lot of slag, impurities, and unwanted elements in the steel.
As an example of unwanted containments in the steels of the age, this is a 1996 "core" assay of a generic WW-I era 1898 Mauser receiver:
Carbon: 0.29%
Sulfur: 0.022%
Phosphorus: 0.019%
Manganese: 0.45%
Silicon: 0.16%
Nickel: 0.05%
Chromium 0.02%
Molybdenum: <0.01% (trace)
Vanadium <0.01% (trace)
Copper 0.17%
Columbium: <0.01% (trace)
The 1996 "core" assay of a WW-I era 1898 Mauser bolt:
Carbon: 0.18%
Sulfur: 0.018%
Phosphorus: 0.014%
Manganese: 0.76%
Silicon: 0.23%
Nickel: 0.29%
Chromium: 0.06%
Molybdenum: <0.01% (trace)
Copper 0.15%
Aluminum: 0.02%
This is the German material specification:
source:
Rifle and Carbine 98 Dieter Storz
Barrels and Receivers:
Carbon LT EQ 0.40%
Silicon LT EQ 0.30%
Manganese LT EQ 0.90
Phosphorus LT EQ 0.04%
Sulfur LT EQ 0.06%
Copper LT EQ 0.18%
The nickel, aluminum, chromium, molybdenum, vanadium, columbium are containments that crept into the steel ladle, either through scrap, or in the natural ore and the Germans were not able to remove them by blowing oxygen through the steel, as was done during the Bessemer process. The copper is in there to make the steel easier to machine, but copper in steel weakens it. A spectrum of unwanted elements and slag is a characteristic of the plain carbon steels of the late 19th and early 20th century.
So, the summary of this, the same historical action designs, made of modern alloy steels, made on modern productions lines, with modern process controls, are going to be more consistent in material properties and stronger than when they were first designed and manufactured 125 years ago.
I know modern high wall M1885 actions were made in 30-06 and 270 Win, so these actions are plenty strong. I also suspect the low wall is a very strong action, but I don't have a low wall to examine.
Anyway, my Japanese made M1885 is a beatiful, finely built rifle and I have no doubt that I could shoot very heavy 45/70 loads in it, loads that would probably create excess headspace in historic M1885 actions.
260 had 60k max psi similar to 5.56 which most everybody shoots all day everyday in 223 rifles.
So is that a good max rule of thumb, 60k psi?
The limiting factor is the load the structure is carrying. Multiply psia by surface area and come up with pounds force. A 260 Rem cartridge is much wider, longer, has a greater head diameter than a 223. So while the 260 Rem and 223 Rem both operate at similar pressures, the 260 Rem puts much more load on the structure. If the action is safe for 260 Rem, than any cartridge which puts an equal or less load, should be perfectly safe.