Lyman 575213 casting oversize bullet

[patio]

Is it possible that a Lyman 575213 minie bullet mold would drop bullets at .582 to .583 in diameter? Did a casting session yesterday and today using pure lead heated to 800 degrees F. All ladle poured. Mitutoyo micrometer used to measure the diameters. Both days the diameter of the bullets were consistent. Today I added a Lyman 575213 old style minie mold and these measured out at .575 to .576. Casting setup and lead used was exactly the same. I am stumped. Any suggestions as to what is going on?

Thank you,

Pat

[John Bly]

Are the bullets round? If not then look for something holding the mold halves slightly open when closed. I could be a sliver of lead or burrs around the alignment pin holes. Lyman molds vary a good bit in diameter from the intended diameter but 7 or 8 thousandths is a bit too much.

[patio]

John, thank you for your input. Yes, the bullets are round, within .001? - .002?. There is nothing on the mold block faces preventing them from closing. When the mold blocks with the handles on and the core pin out are held up to a light source, very little light gap between the block halves show. There is some light gap maybe .001? or so.

Regards,

Pat

[PoorJack]

In answer to your question- YES it is entirely possible for a 575213 to cast at .580+. Just because the mold is marked as a 575213 doesn't mean it's going to cast at .575. That's due to a number of factors- temp, lead alloy, technique, and not the least, manufacturing tolerances. A mold is cut with a "cherry". That cherry wears as the mold production run is completed meaning, early cut molds will cast at larger diameter than a later mold in the run. This is a well known phenomenon and why you use sizing dies to achieve a certain, desired, final dimension. I have 2 of these molds and they cast to different diameters. One is .575 the other is .578.

So don't sweat the bullet being too big. Get a sizer from Tom Crone or NE Trader and size the bullets to what you want.

[John Bly]

While searching some years ago to find a 575213 that would cast a bullet that fit my rifle without sizing I went through 4 or 5 before I found the one I was looking for.