Thanks for the reply BA. I see what you're saying. I was pretty impressed with 2" groups at 90yds with a 44 Magnum rifle, because of a prejudice I have that pistol-caliber rifles shouldn't be that accurate. This results in my being impressed/suprised when they are merely reasonably accurate. I really should have known better, because I have handguns that are that accurate, and there's no reason to think a carbine would be less so, when it has a longer barrel and is easier to shoot...
As far as stability of the bullet, I think you are right in your descriptions, but I also harken back to one of my instructors who taught us a technique for long-range pistol shooting wherein we imagined the pistol's sights and barrel are in a pipe, and if you hold correctly, align the sights correctly, squeeze the trigger, and have reasonably consistent and accuracy-supporting fundamental skills, one can shoot very respectable groups at virtually any range. Applying the same principles to closer-range shooting results in ragged-hole groups.
The modern-day experts I'm speaking of when I describe sizing bullets to chamber throat diameter are folks who write for Handloader magazine, like Mike Venturino, Dave Scovill, and Brian Pearce. I know some here don't think much of any gun rags, including Handloader, but they are about the only ones who publish any articles about casting that go beyond "buy such-and-such brand commercial cast bullets." They actually talk about casting, moulds, sizing, loading techniques, etc. By the way, the example I used in my post above was an exageration, but it illustrated my point.