Hi all, I cast up a bunch of lyman .224 cal bullets out of about 15% antimony lead and found that the gas checks dont really fit on. I did a bunch out of plain wheel weights and all was well. Any ideas?
I want to fire them in my Weatherby .224 mag fairly fast so wanted them hard.
While putting together my other post, I forgot to address the original question. Yes, as others have said, it relates to the different shrinkage of hard and soft alloys. Antimonial alloys shrink less than pure lead, and the harder the alloy the less the shrinkage nd the bigger the bullet.
Obviously your bullet is a close fit to the gas check when cast (relatively) soft. So close in fact that the slightly bigger diameter of a harder alloy is enough to prevent fitting the gas check.
It is not unusual. Moulds are made to tolerances, and I have measured as much as two thousandths difference between two identical moulds. I have two 30 cal moulds. The Hornady gas check is a push fit on one and loose on the other. Some moulds are so undersize at the gas check shoulder that the gas check won't crimp on. The remedy is to bore out the mould on a lathe. There are two possible remedies for your oversize shoulder. The easy one is that a another make of gas check might fit, eg Gator instead f Hornady. The other, is as recommended by others, expand the gas check.
Under no circumstances soften the alloy as has been suggested. Despite some claims to the contrary, a hard alloy is better for high velocity. 15% Antimony is harder than linotype and probably unnecessary, but can do no harm. Stick with it and see how it performs. With gas check you can rely on it doing 2500FPS with no difficulty. Probably a bit more, and I know of a 375H&H rifle that clocked 2700FPS with no trouble. The limitation will be that, for various reasons, cast bullets can become wildly inaccurate above 2500FPS.