My comment was solely referring to the human discomfort of shooting any reasonable load with those powders in a Contender. A friend of mine had to try that in his Contender and predictably got rid of his 45-70 barrel.
I'm aware of the frame stretching issue with Contenders and the .45-70, so I've been keeping close to the starting loads. My Sierra and Hornady books even have dedicated handgun loads listed, with Hornady noting they got best results from H322.
I also get a kick out of the comments in the Hornady book about "severe recoil and wear and tear on both the shooter and the firearm..." (and I'll wholeheartedly agree with their assessment).
The other thing I find interesting is in the Sierra book. The description in the pistol section states "Loads reduced below these are not recommended". But when I turn to the Trapdoor loads in the same book, every powder listed has a lower starting point than the "do not reduce below" pistol loads.