Re. many original howdahs being chambered for the .577 Snider. This appears to be the case. But there also appears to be Howdah pistols with shortened variants of the 577 Snider. I'm thinking the full Snider might have been a little too much, and lesser recoiling variants were created and purchased.

I've never shot a .577 Snider in rifle or handgun, so don't know.

Is anyone here who shot Cal Pappas' .57< Howdah? Was it the full sized Snider case?

In our modern handloading times, of course we can load down a case to make it more manageable. In previous times, often a BP firearms would have BP hand loading tools for the brass cases in its gun case as well.