Let me try to address some of the questions one at a time, and keep in mind that this is my friend's setup, so I don't have his notes or anything; I must rely on my increasingly hazy memory.
Teichi: He's using once-fired factory brass, which he bought new and fired himself in his rifle and pistol. As to bullet weights, primers, etc, I don't remember, other than that everything was good to go. I.e., the bullets and primers and everything are the correct caliber/size. All brass was checked and verified to be within spec for case length. I don't think we've got wrong components, but it's a good idea to check.
Heavies: The scale is definitely a PITA, but I'm 99.X% certain I was reading it correctly; the fact that it's so darn difficult to use made me look at everything several times, re-verify zero, etc. It definitely throws things off if you move the scale at all, I will have to ask him if he thinks that may have happened. When I thought it was just the rifle rounds that were overpressured, one of the first things my Pops mentioned was OAL and the possibility that the bullet could be pushing up into the lands. When I get back over to his place to so some reloading we'll make a simple chamber gauge like the old man had to make sure that our length isn't causing the problem. I wouldn't think that should have happened with multiple rounds in two different calibers, but I suppose anything's possible! I didn't realize that too much crimp could cause overpressure; how do you verify neck tension on a pistol cartridge? I don't remember what number he told me for neck tension on the 270, but it was lower than we would have liked, I think around two thousandths or so. I wasn't there for that part, so I don't know if that's a measurement error or if they were really that loose. The bullets didn't set back into the case with hand pressure, so I figured they'd be all right so long as he didn't subject them to any craziness like dropping the box or something. I suppose bullet set-back could have been an issue with the rifle rounds, but we loaded and fired them one at a time, and he said he was very delicate in handling them. I don't know. As for the autodisk, it did fine with the pistol powder; but the rifle stuff he's got (which I can't for the life of me remember the number, it was IMR powder that the Hornady manual recommended for .270) is about the size of rice grains, which is why I think his thrower didn't want to drop an accurate charge; too much cutting and whatnot.
It could be that the rifle rounds set back, and the pistol rounds were crimped too tightly, I suppose, but I'm thinking that Occam's Razor dictates that there must be one thing common to both calibers that's screwed up. Once he verifies the scale, I'll let you guys know what the result was, and we can go from there. If it's not the scale, it must be something in our process, so we'll have to go through one step at a time and figure out where we went awry. Thanks for all the suggestions!