Interesting. If you have a minute, would you mind explaining (in the thread or via PM)? I'm interested in how this works.
What would the benefit of a longer cartridge be if the muzzle velocities were the same, other than lower action pressures? My action is limited to trapdoor pressures, so I'm capped there. (28 000 CUP I believe... going by memory).
It's a 71/84 action by the way, that is now permanently single shot.
As it stands I'm not sure the action would fit a 45/90 as well. I can't find anything on the average OAL of 45/90 to get a ballpark idea of if it would fit when loaded up (and I have yet to buy Cartridges of the World)
It's a M71/84 action? Why not stay in 43 Mauser? It has 20% more capacity than the 45-70 and about 8% more than the 45-90 - it's in the range of 458 Win Mag, capacity-wise (but not pressure-wise!).
The larger the capacity of a cartridge for a given bore size:
- the lower the pressure for a given bullet weight at a given MV; and/or
- the higher the MV for a given bullet weight at a given pressure.
The 28K psi comes from the upper limit of a Springfield Trapdoor which is not near as strong an action as the M71/84, but it's a sensible upper limit. With the 43 Mauser, you can use Trapdoor loads and never test the action strength, in fact you'll be well below 28K in every case, since the 43 Mauser case has 20% more capacity than the 45-70. I load up to 100 fps above Trapdoor loads, but always seem to find the best loads for accuracy below that, typically over H4198.
