I ordered this .312" mould today from Brownell's.  I figured the 155 gr. round-nose would be a fun economical plinker at 50 and 100 yards in my Krag "carbines".  It will also conserve lead alloy.  Now, I'm off to scrounge for wheel-weights.  The learning curve begins!  Thank you everyone for your helpful leads.  Any opinions on the suddenly ubiquitous aluminum gas-checks?  Parashooter's recent photo of rifling nicely 'engraving' a cast bullet and its copper gas-check gives me pause to try anything but copper in this role.