quote:

I did a stress analysis on how much pressure my 45/70 handi rifle could take, and I proved to my satisfaction that it can take more than the brass. When I posted that on Marlin Talk, someone said my analysis was worthless, so I did a test to validate it. I chose Unique powder because it is a fast pistol powder that, in large quanities, gets the pressure very high. note, the same guy said my test is worthless, so a real lesson is should be learned from that about on line discussions about pressure.

45/70 work up with; 405 gr cast with lube bands, CCI 200 primers, Win brass, old Unique [dirty] powder, chamber well lubricated between firings with CLP for max bolt thrust.

Quickload calculation of pressure and velocity with 405 gr, Unique

shot 0) 15 gr, 24,700 psi, 1271 fps, no shot fired, listed for Quickload reference point only
shot 1) 18 gr, 33,217psi, 1403 fps, primer looks fine.
shot 2) 20 gr, 39,435 psi, 1485 fps, primer is fine
shot 3) 22 gr, 46,133 psi, 1563 fps, primer looks flat.
shot 4) 24 gr, 53,334 psi, 1637 fps, primer is flat.
shot 5) 26 gr, 61,067 psi, 1709 fps, primer is top hat and flowing, action popped open and case ejected on firing
shot 6) 28 gr, 69,366 psi, 1778 fps, primer is top hat and flowing, case head expansion .001", action popped open and case ejected on firing
shot 7) 30 gr, 78275 psi, 1846 fsp, case head expansion .0015" action popped open and case ejected on firing, some leading in the muzzle.
shot 8) 32 gr, 87,841 psi, 1911 fps, case head expansion .0025", case head separating where case head is flowing into the extractor, action popped open, some leading in the muzzle, and case ejected on firing, primer is spreading out .010"

There was no change in headspace, but I had to stop the work up because of case head separation where the case head flowed into the extractor.

Reference loads:

1) "Loads for the 45/70" from the H.P.White laboratory via "American
Rifleman" 1950~1968 via "NRA Handloader's Guide" 1969 says:
405 gr Rem S.P., 17.5 gr Unique, 1286 fps, 25,240 pounds pressure, for 1886 Win

2) "Lyman's 47th" 1992 says:
400 gr cast, 16.5 gr Unique, 1286 fps, 27,000 cup, for 1886 Win

3) "Lyman's 47th" 1992 says:
385 cast gr cast, 17.5 gr Unique, 1411 fps, 38,500 cup, for Ruger #1

From left to right, not fired, shot 8, shot 7, shot 6, shot 5, shot 4, shot 3, shot 2, shot 1 -

There was a lot of leading on the last few shots.