If you convert what is on the bbl of the 45-70 to psi, it comes to 28,800. The same as what Remington said.

Speer, Lyman, Accurate, Alliant, Vihtavuori, Hodgdon and Hornady all offer data with pressure info that puts this round well above recognized "Trapdoor" loads.

I have both guns and have done extensive load testing with both. None of the below loads showed any signs of pressure. No flattened primers, cases just fell out etc...

30-06 180 grain jacketed at 2600fps and 220 grain jacketed at 2400fps, both with IMR4350.

45-70 350 grain jacketed at 1800fps and 405 grain jacketed at 1700fps, both with Reloader 7.
Used various lead (gas checked and not) bullets with results slightly faster than jacketed.

I've also came up with some loads that were faster that were "safe", but went back to the above loads for regulation.

I don't have a dog in this fight and do not wish to. Just stating what I've done and found.

Mike