I was trying to convey to OP the usefulness of rebarreling his to .357 Max. Here is an interesting report of such an animal , in a CVA Apex .
https://dandtcustomgunworks.websitetoolbox.com/post/357-max-test-5264779
The first few that come to mind have already been mentioned, the 30-40 krag, 7x57r, 303 brit, etc. I like the idea of a 35 whelen, and maybe even 500S&W for a cannon cartridge...
Can you get 50-70 brass? That would be better imo if the brass is available, I just haven't seen any in a few years.I prefer the idea of .50-70 over .500 S&W.
- It has history and even the original military load (with smokeless) will do what a factory .45-70 will do.
- You can load it with black powder and duplicate that same military load.
However, since the bullet diameters are not the same (.515"/.50-70 and .500"/.500 S&W) you would not be able to source .515" jacketed soft points, meaning that higher velocities would be more limited.
Still, a 500 grain gas check cast bullet from a custom mold at 1600 FPS would be pretty potent.
Can you get 50-70 brass? That would be better imo if the brass is available, I just haven't seen any in a few years.
For those that don't have a Ruger No. 3, it should be noted that it has a crescent like steel butt plate, and is not ideally designed for high recoil cartridges.
They are also not the easiest platform to scope (eye relief issues due to the forward mounting of the scope rings – there is no rear receiver bridge in a falling block). That’s why I asked if the OP intends to put an optic on it - there’s no sense chambering the rifle for a long range cartridge if it’s going to be shot with iron sights.
I enjoy shooting both but the one #3 that I fired in 45-70 was just not a fun gun to shoot. The .375 Winchester would be a good chambering but still more recoil than I would like in that lightweight rifle.