Points all taken.. Larry & Outpost alike.
I hadn't considered the old balloon head brass likely playing its part in that old '58 cast manual that says 7.5grains unique. That point makes good sense now that you mention it. I believe I will make a "consideration" note inside that manual of mine for future... wherever & for whoever ends up with it after me down the road.
I'll work to 6.5 once I get going on this myself, see what the chrony says and keep that number in mind for tops far as the auto-rim load will go.
And to Outpost specifically.. those rockwell numbers are interesting to note too. I have had a few measured of my own, Colt single actions, and they've run anything from 14 to 28 themselves ... the raw steel below case their hardening. Hardened, I had a privately operating metal-guy claim his own three-time sophisticated set of heat treat brought one particular frame to 38, but I don't know whether that was surface measured after casing, or if it was an alteration to the actual metal composition and he meant the steel for a considerable depth below. He was an unusual kind of genius, the kind that are so smart they're hard to talk to.. if you know what I mean. Odd duck to say the least. I didn't want to throw the lot of what he said out the opposite ear after he told me, because Dick Casull is said to have done similar in the 50's. So who knows. Makes for good conversation. These rockwell numbers and steel datas aren't widely discussed, so some guys following this thread may find that all of value too.