Light cast weights

[JACCO]

I'm new to both reloading and casting so please bare with my ignorance. I recently purchased a 450 sizer with dies, a lyman melting pot, a 4 cavity Lyman 452630 mold and a rcbs 38-162 swc mold along with some lead ingots that had 15 bnh written on them. I melted the ingots and after several attempts I made some nice looking 45 and 357 bullets. The 45's weighed out at 200 gr, BUT the 38/357 only weighed 143.8 grs. It is a gascheck mold, so not knowing what a gascheck was, I orderd 1000 of them and with the gas checks I'm at 147 grs. Any ideas why they are so light? Also would I be able to size those down to 356 and use in my 9mm?

[theperfessor]

Welcome to the forum JACCO.

1. Does the bullet look like what it's supposed to look like? Maybe a mis-marked mold or box. Or maybe the bullet is too short for some reason. Were the molds new or used? A used mold may have been refaced a little to clean up the top or lighten it up. A new mold may not have been machined correctly. It's not unusual for a bullet to vary in weight from what is marked, and different manufacturers base their bullet weights on different alloys. Weight variance is the accumulation of manufacturing tolerances and alloy tolerances. But yours does seem rather light. Got pictures? Post 'em, we'll all try to help.

2. My Hi-Power loves .3575-.3580" cast bullets. Read some threads and you'll find a lot of people who own a variety of 9mms endorse cast bullets in this size range. But even if you did need to size them down, the problem would seem to me to be more a matter of feeding properly - and if the required seating depth intrudes into the case enough to swell it at the base of the bullet and/or raise pressures from reduced combustion chamber volume. Can you do it? A big maybe on that, but if you got everything already why not give it a try. Start low and work up as usual.

[dicko]

The 45's weighed out at 200 gr, BUT the 38/357 only weighed 143.8 grs. It is a gascheck mold, so not knowing what a gascheck was, I orderd 1000 of them and with the gas checks I'm at 147 grs. Any ideas why they are so light? Also would I be able to size those down to 356 and use in my 9mm?

From memory, the 452630 is a 200 grain SWC, so the alloy is about right. I'm not familiar with the RCBS 162 grain bullet, I'll need to look at the on line catalog. A gas check bullet will cast three or four grains light, to allow for the gas check weight. I suspect that the mould is wrongly marked, and that what you have is the RCBS 150 grain gas check mould. Note that as cast weight will often, in fact usually vary slightly from nominal weight for two reasons. First, the alloy gets harder as more antimony is added, but also gets lighter because antimony is lighter than lead. Second, there is some tolerance in moulds, so that ten identical moulds can easily cast ten different bullet weights. The variance is usually not great, usually not more than one or two grains, but I have two identical Lyman 9mm 130 grain moulds that cast four grains different with the same alloy. That's why trying to blend the alloy to cast the exact nominal weight is not a good idea. Because, if a mould casts light, you can only make it cast heavier by reducing antimony content. That makes the bullet softer with the risk of heavy barrel leading. The rule is, get your alloy mix right and accept that the resulting bullet weight might be slightly either side of nominal.

[JACCO]

Thank you both for your replies. The bullets look fine so maybe the mould is marked incorrectly. I just orderd a hardness tester and the newest Lyman cast bullet handbook. I'll try to blend to a "known" bhn then cast again. If they still come out as 147, then I'll just shoot them as 147. I'm sure there's load data available. Thanks again

[MtGun44]

"Size down to .356 and use in my 9mm." -

Have you slugged your 9mm? Most 9mms do very poorly with .356 diam boolits, and need
.357 or .358 to work well.

Bill