Subs and Moulding
Doc,
BLE is right, the subs were made in such a way as that they would deliver a similar charge to BP when measured by volume. The idea being that most ML'ers use volumetric loading practices.
If you are getting "flashing" on the side of your cast bullets, I wouldn't bother using clamps to hold the blocks tighter. It will slow your process, cool the mould blocks and fail to solve the problem.
Usually flashing on the side, or a mould line on the bullet means that you have a small amount of lead that has creeped onto the face of the mould block - either in the mating groove or on the flat. This prevents the blocks from closing completely and leaves a microscopic gap.
Check for a small bright silver-sish spot on the face of your mould blocks. I use either a hobby knife (carefully now...) or some fine steel wool to remove any errant lead on the mould block face.
Also, if this is your first experience casting, there are some excellent resources on various forums about casting. I am by no means and expert, but have been working on it for some time. Mould block temperature is a critical element, so if you can get the mould to a consistent, hot enough temp, you are well on your way.
Cheers,
chowmi