I'm seeing people on the interwebs with all their wisdom stating Winchester/Miroku rifles are good up to 50,000psi. Hope I could verify that...
Back to the drawing board, I guess...
I would never load an 1886 to 50,000 psi. I don't think there are any credible sources publishing data in that range other than for strong single shots. The strongest commercial loads I know of are made by Garrett Cartridges. Their Hammerhead ammo is loaded to something like 35k cup from what I remember. I believe that they state their ammo is ok in newer 1886's.
To give you an idea of some of the dangers I will give you two examples from some time ago. Both happened to me. The .45-70 was the first cartridge I'd reloaded so I was not very experienced when this happened.
1. I was loading using data from the Lyman handbook. I was using their data for Reloder 7 and 405gr cast bullets. I never went up to max loads, always staying a grain or two below max. One day I bought a chronograph and decided to check velocities. At Lyman's starting powder charge I was hitting max velocity but in an 18.5" barreled marlin. I spoke with Alliant to ask why this would be so. They told me that the powder had been changed since they bought out Hercules who made the original Reloder 7. They said what I was seeing is what they'd expect and that Lyman was publishing data using the old powder. Have no idea how fast the heavier loads were going because I disassembled them.
2. At this point I'd been loading .45-70 for a year or so and was still into shooting painful .45-70 loads. One day I decided to try some of Hdogdon's loads in my Marlin. They were not max loads, somewhere in the middle of the range for lever guns using H-4198 and I don't remember the bullet, but probably 400gr Speer. I'm quite meticulous so no errors in powder charge, same oal, primeds, brass, etc. After shooting the loads I deprimed the cases and found that my RCBS Rock Chucker could barely resize the brass. It took huge force on the handle. The resized brass had a ridge in it near the web where the die had reached the end of its travel. The web of the brass had significantly changed diameter. I was really lucky that my rifle didn't disassemble itself. That was published data with brand new brass.
The internet is full of pictures of disassembled rifles, mostly Marlin 1895's in .45-70 that were pushed too hard.
One other thing I found with my chronograph. Case volume is very significant. if you try thicker brass like Federal or Remington with data specifies Winchester brass, you'll have to back off the load significantly.
Nowadays I mostly shoot black powder cartridge rifles, but when I shoot smokeless in my Marlin it's mostly under Sammi pressures, except for the cartridges I keep for grizzly defense. Those are 405gr cast bullets at 1700 fps which can be achieved with reasonable pressures for a modern lever gun.
Chris.
