Aside from possibly giving me poor accuracy are there and other concerns that I should be aware of when shooting an undersized cast bullet? I have a Lee mould in .457 and with straight wheel weights the bullets are .452 or .453. Would a good alloy produce a different size bullet? Thanks, Mike

that really is unusually small for a .457" mold to drop bullets. If you really need .457-458" and use .453" bullets, would expect a leading problem. WW's are pretty tough, and tend to cast out LARGER than softer alloys.

Putting a .453" bullet through a .458" bore would tend to let gas squirt around the sides of the bullet, eroding lead with that high pressure jet of gas, If you could smack them in the rump with sudden high pressure, might get them to slug up to size...which is a trick BP does pretty well with dead soft bullets, but with WW's it would take a very high pressure wack,

If your readings are right (and it might be that your micrometer/caliper is off), that mold just might not work out for you.

NOTE: Ribbonstone posted while I was composing, so some of this is redundant.

That's an awful lot of difference to be an alloy problem. I would wonder what you are measuring with, first? Some calipers can be off a couple thousandths. Use an OD thimble micrometer.

If the micrometer tells the same tale, call Lee and I'm sure they'll replace it. It could have been gauged with the tool intended for .452 molds.

Except when the bullet is REALLY soft and the powder is really fast (like black powder), lots of bad things happen when your bullet is that small, such as no accuracy to speak of and incredible Leading.

Test your measuring device against something trustworth in the same size range. Most cheap electronic calipers I have tried are off by at least .002".

CDD

I wonder if it is really a 45 ACP mold. What kind of bullet is it?