I managed to rather easily and quickly get through to Hornady tech support. The support technician had a very different perspective than me on this whole situation.
He said the limiting factor on testing handloads when firing a replica 1873 Peacemaker is the crappy sighting system. He was amazed that I got the Trail Boss load with hard cast bullets to shoot 1.5" to 2" 5-shot groups at 25 yards using those authentic 1873 sights. He actually asked if I somehow used optics.
He said he would have expected me to get 4" groups at best with that firearm with any good load, but of course he is not ever going to say his company's bullet is inferior.
He said the std Dev of 9.7 was excellent for a cast bullet in a light CAS load, and proves, surprisingly, that there is no "too little powder in a large case volume" issue.
he said that getting over 800 fps with my 4.75" barrel length versus 900 fps for Hornady's 10" barrel length, was what he would expect. (And remember i am not getting excessive leading, but instead actually got a pretty clean barrel after the lengthy shooting session.)
He said he admired my setting the higher goal of 1.5" to 2" groups like I got with the hard cast bullet when I did MY part, but said that was unusually good grouping, especially given the sights, so I might need to try a number of bullet and powder configurations to reproduce that kind of result. He does not regard it as being typically attainable with these replica handguns.
He said He says a .003" crimp effect on cast bullet handloads is a good target for crimp, and my .3578" average virgin bullet OD being reduced to .355" is a .0028" reduction, which is within that range. He personally would like to see maybe a .356" seated and crimped bullet OD, but the .355" does not shout "problem" to him.
But he also agrees that if I want to try it, loading the fired cases withOUT resizing would be worth trying if I am determined to chase a better group size, and have or can get the hardware to enable that. But he says he certainly would not spend a lot of money on that because the firearm's sights are the limiting factor here, not the ammunition. And, he said, I should record the exact setup I have right now because it is a good one from his perspective.
His point is decent, because while I can take many seconds to try to align those crappy sights as well as I possibly can when doing ladder testing, in actual CAS matches, where the TIME spent on shooting a stage is far, far more important than accuracy that is simply good enough to hit the target ANYWHERE on it, I will not be able to take the time to do that alignment. The good CAS shooters shoot an entire 5-shot cylinder in what, maybe a couple of seconds? But my thinking is that the more accurate I can make the ammunition, and the more error I can separately yank out of the now-proven sight windage and elevation errors, the quicker I can fire strings of shots with higher confidence that I will still be able to hit the metal targets.
So, I'm going to do some experimenting to see if I can successfully load ammo using the un-resized cases, and see if that changes anything for the better.
Jim G