Thanks for that info Daryl.

As I stated in the previous post, the flat base 405g PP bullets didn't shoot all that well, so I thought I'd make some improvements and ended up making a whole new mould and go from base pour to nose pour as well.
This is the result.

The mould body is made from a piece of .243 Stainless barrel shank.
It fills nicely from a bottom pour furnace, with the sprue plate held against the nipple and the bullet falls out of the mould with out any difficulty.
I'm completely satisfied with the resulting bullet. It has a perfectly flat base that is perpendicular to the central axis.
I made it to cast at .410" so they can be tested in a .416 Rigby, as I'm really happy with the RCBS 40-400 bullet for my 450-400 and don't need another PP bullet for it.