I'm trying not to ask too many questions too fast ...but here's my next one anyway (and I'm open to wild opinions, conjecture, hard facts, and experience here):
1. From what I understand, low velocities/low pressures (without gas checks) should use softer lead bullets so the bullet will be able to obturate properly and prevent blow-by and leading. Makes sense. The corollary is that harder lead alloys used at low pressure/low velocity can result in leading due to blow-by. Real life evidence seems to support these relationships. Harder lead requires higher pressures in order for it to obturate correctly.
2. Gas checks are always a good idea but not always required.
My question is this ...Is it OK to shoot soft lead at higher pressures/velocities? It seems to me that it would obturate just fine at the higher velocities and that if the bullet doesn't cause fouling due to friction at lower velocities, then it shouldn't at higher either. No blow-by and no friction issues should equal no leading issues if shooting soft lead at higher pressures/velocities. What am I missing here? I thought someone said not to use soft lead at higher velocities ...why not?