Before purchasing a mould, plug your data into this twist rate calculator on "Berger bullets" sight to confirm stability. When I bought my .500 BPE last year it came with a box of loaded ammo than had 440GR woodleigh bullets. I had no intention of shooting someone else handloads so I pulled the bullets and dumped the powder and reloaded them with a load that I KNOW what is in there. My research showed that Alex Henry .500 were intended to shoot 300-340GR bullets. I checked the rate of twist and found it to be 1-38", much too slow for a 440 gr bullet. I bought a mould from NOE that throws a 325GR slick bullet (@ 20-1 lead/tin) and according to the Berger bullet calculator, my rifle should provide great stability for that bullet. My preliminary tests suggest this to be so as, at a particular powder charge it put 5 out of 6 shots in one large but ragged hole @ 50 yards.