Do bullets "grow" after sizing??

[1bluehorse]

Here's my question...if you take (for instance) a .432 as cast boolit from #2 alloy and an as cast boolit from WW (same size) and run them through a .430 size die, would they not both be sized to whatever the nominal size of the die is..? AND will they (for all practical purposes) stay that size....If this is so, then why, when I order a .430 size die they always come out sizing .4293/4 ..I've talked to Magma and told them I wanted the "die" to size a boolit at what the die says..ie: a .430 die= a .430 boolit and so on...."well, send me a sample of you alloy"....why? What am I missing here....I understand different alloys cast different size boolits as cast, along with heat, methods used etc; but what does that have to do with the sizing die.....? I asked them to just hone, ream, whatever to the size I request.....431, .458, .358, and .430....actual, I'll worry about the rest...thanks....this is in no way meant to degrade, slander, or otherwise demean Magma Engineering, they are nice folks and will certainly go out of their way to help their customers...I'm just confused about the sizing issue.....can someone straighten me out in "sizing for dummies" lingo..[smilie=l:

[seaboltm]

I would certainly imagine that exact alloy composition as well as casting heat, quenching techniques,etc. all effect a lead castings properties. It is easy to imagine that under certain conditions an alloy could spring back a bit after sizing.

[Oreo]

Yes, different alloys will have different plastic deformation thresholds. Also, a ten-thousandth of an inch is "a slippery bugger". So unless you're paying ($$$) for that kind of precision you should expect a more reasonable tolerance when ordering custom dies.

[Calamity Jake]

If your size die is sizing undersize with your alloy then lap it out or send it back for repair.
Most alloys will grow up to .0005-.001 or maybe a little more in size with age, the harder alloys grow the most.
I let all my newly cast boolits age for at least 10 days before I size them.
Some alloys spring back after sizing, some don't.

[cbrick]

can someone straighten me out in "sizing for dummies" lingo..[smilie=l:

Sure, the percentage of Sb in the alloy and to a lesser extent the percentage of Sn will determine the as cast size. With just about every caster using a somewhat different scrap lead alloy the folks that make sizing dies must have either white hair or no hair. That's why he wanted you to send him a sample of "your" alloy however, if you only have a little of that alloy don't bother, if you'll be using a different alloy next month it won't come out the same as this alloy.

All is not lost though, simply order yourself a .431" die. Then if you change alloy's and the .431" is bigger than you like just use the .430". I have 35+ Star dies across several calibers and I can always get within a few tenths of my goal and trust me, tenths don't matter. No, you probably will never need 35 dies but I've been buying them for a few decades now and they do seem to accumulate.

On the bright side, you'll probably be happier sizing to .431" anyway unless you have very tight throats.

Rick

[1bluehorse]

Thanks for the responses guys (and gals if applicable) so, what I'm walking away with is....the same properties or lack of, in an alloy (discarding the casting method, heat, etc;) that will make/allow it to drop as cast larger/smaller than a different alloy will also have the same effect on a sized bullet?? Am I reading this correctly....I didn't think that would happen....I figured when a boolit was sized to a particular size..it stayed that size...I'll be darned....and I'm with you cbrick, I have .430, .431, .432 sizers, BUT they all will size a hair under using WW and a bit of tin....oh, well.....

[bhn22]

I've had the same issue in the past. My solution has been to order the size I want, then test size a few and measure the bullets carefully. They are almost always undersized, but I expect that. At that point I lap the sizing dies until it pleases me. I've found Lathesmith, a vendor on these boards, does a much better job of getting me what I want sizewise than Magma. You should seriously consider him. You should have heard the conversation I had with Magma when I wanted a .453 sizing die. You'd think I was asking for the moon. They offered a .454 die that would be slightly under .454. The die they sent was .454+. Now my original .452 die, which actually came out .451, is .4525ish, and works perfectly.

[Wayne Smith]

If you actually have access to accurate measurements of .0001" then pay attention to what Oreo said about plastic deformation. This refers to spring back after sizing and this will change with composition as well. It affects the diameter of the final product.