Forgive me if it sounds like I'm talking a load of bolloxxx*, but I am not nor ever have been a reloader. But I know how nerdy this tribe of humanity can be. In respect to Colonels thread 46, surely if what you're getting is boat tails and what you want is flat base, it'd be simplicity itself to make a shaped cup thing to hold/support the bullet and a press thing to simply press the boat tail shape into a flat bottom shape. It's only very malleable copper and lead we're talking here. Bullet might end up a bit shorter but........
* Bolloxxs; REME technical term. Generally used as a term of frustrated expression to another hapless individual who appears to be talking an load of crap. As in '........that's a load of bolloxxs'. As used on a regular basis by Infantry too. BAR and Muffer will have used this term