"This was when the idea was that the lube was the big failure when it was really overall fit. Of course some of the lube back then was water pump grease..."
My favorite load manual is the Lyman Cast Bullet Handbook from the 70s, tends to be my go-to for most things, but throughout the whole thing, they tout always sizing to groove diameter. Talk about a recipe for gas cutting and leading.
I was at a gun show in Wichita about a month ago, an old man who had been an avid handloader was selling off a lot of stuff and I bought a few little things. He had boxes of good cast bullets, which normally I am interested in, but all of them had been dutifully sized and lubed to groove diameter (bunch of good .45-70 bullets, all sized to .457). Had to pass, don't need the aggravation of leading. Bad thing is, someone who doesn't know anything about cast will buy those to load, will just load them like jacketed and get the crappy results we know he will and then the myths about cast bullets will continue to perpetuate in the gun community.