Here is my Handi Rifle 45/70 work up test data after I did a max pressure analysis of the rifle [with the help of my father, the gun designer, and also help from a mechanical engineering professor]:
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"
After this break action test I did similar work ups to the limit of rimmed brass on sav 219 30-30 and Stevens 410 with 45 Colt.
The 410 choke split with the 405 gr .458" bullets. The 410 stock butt was against concrete. The recoil forces splintered the 410 Birch stock wrist.