Ran into the issue with torn metal again on my bullet bases. No way this was due to a cold mold, because with my amazing Lee rocket pot, I was on the high side of 750 at the start.
About 1/3rd of the way through the session, I poured, then did a slow count to ten before whacking the sprue. Yes, I was turning the amazing "little supernova" down, but since 15 pounds of lead hold heat, the delay in dropping the boolit was needed.
With the slower cadence and (eventually) lower lead temperature, the sprue cut-off on the bases looked like... a cut-off sprue. I need to tighten up the sprue plate a little bit, but most of the bases were level.