I wonder if the man was on to something... I just came back from the range, shot some cobbled-together PP rounds today - the bullet was harder than a woman's heart (50/50 lynotype/lead), patched to groove diameter, about 540 grs.
this was patched to groove diameter, seated quite deeply in the (45-70) case, compressing the 67grs of swiss 1 1/2grs quite a bit, without lube cookie, just a card overpowder wad - I only lubed the visible part of the patch (about 1/2" at most)
I shot 10 of these with just blowtubing between shots, and I was extremely surprised at the accuracy I got - I did have a horizontal spread, partly due to me no doubt, but these bullets sure wanted to group! Even the very last shots were showing no loss of accuracy at all!
What's more, when cleaning the barrel after 10 rounds, I was very much surprised at the lack of fouling in the barrel - actually much less than when shooting GG bullets. Basically, everything was wrong - bullet .451, patched to .458, hard alloy, no lube cookie, no wiping between shots - but it WORKED! I'm puzzled, but agreeably - and I'll try this again, even if I am quite sure after 10 rounds that this isn't a fluke....