Do cast boolits expand after sizing?

[Trinidad Bill]

I sized and lubed(moly) a number of Lee 379-250 boolits to .378 with my Lyman 4500. They seem to measure dropped anywhere from .380-.382.

After shooting this weekend I notice some leading so I started to measure the sized boolits. They seem to have rebounded from .378 to .379 and .380.

Is this normal? Should I be sizing multiple times?

[Shiloh]

Might be a little springback related to the metal you used. Had the same thing happen with some .4o cal boolits.
I did have some unsized unlubed rifle boolits gain about .0003 after several months. I can't give you an actual time that this happened as I hadn't used them for a while. Did this take place after a couple of weeks or a couple of months. Who knows.

Shiloh

[243winxb]

There is some spring back after sizing. Different alloys react differently, more or less. But sized boolits dont grow as they sit over a longer period of time.

[Trinidad Bill]

Might be a little springback related to the metal you used. Had the same thing happen with some .4o cal boolits.
I did have some unsized unlubed rifle boolits gain about .0003 after several months. I can't give you an actual time that this happened as I hadn't used them for a while. Did this take place after a couple of weeks or a couple of months. Who knows.

Shiloh

It was about 2 weeks.

Maybe I need to go down a couple of .001" in the sizing dies. These were COWW (Clip On Wheel Weights).

[MtGun44]

They can change size over a few weeks, but the rebound is near zero, very small
with lead alloys. The alloys like wwts with antimony and arsenic DO expand and
harden with age - days to weeks generally depending on temperature, cooling
rate and particular alloy mix.

That said, leading is not normally caused by too large, but by too small, poor
lube, inadequate lube. Being .001 too large is normally not a cause of leading,
usually is a FIX for leading, actually. I'd bet the smaller ones are leading and
the larger ones are not.

Bill

[Trinidad Bill]

Thanks for the tip Bill... I will take a look at running a batch through as dropped or .380 Laser-Casts. I am assuming that Lyman's moly lube is up to snuff?

[Shiloh]

I shoot as larg a boolit as will chamber. In 9mm They are .358-.3585. In .38/.357, .3585.

My boolits drop at .359-.360. .My LEE push through sizer is slightly oversize and just kisses the mold marks at .3585. wHAT MtGun44 said, undersize boolits rattling down a bore is what causes leading.


Shiloh

[WALLNUTT]

Check your bullet diam after sizing. A .378 die may not be .378.

[JeffinNZ]

Only if you marry them.....

[243winxb]

Every time this question come up, i run down and measure my test batch of boolits to look for an increase in diameter. Not going to this time, as i know they are not growing after sizing. Your results may be different with a different alloy.

[btroj]

Only if you marry them.....

Good thing your wife isn't a member here......

[hickfu]

I actually saw that a boolit that I dropped after sizing had rebounded back to its original size... I didnt think it was possible.
It dropped at .462 and I sized it at .460 (and my sizer sizes to .460) When I found the boolit under my bench I knew it had already been sized by looking at the bands but checked size and it was just about back to .462 (more like .4618)

Doc

[tomme boy]

Mine do when I shoot something with it!

[Slow Elk 45/70]

Yup, that is when they are supposed to get larger. Your problem may be the alloy your are using , check your sizer to see what it really is sizing at......makes it more interesting......Jim

[freebullet]

Them may be some magic beans. Careful where ya plant them.

[44man]

Bill is right. Depending on the alloy and when you size them. If sized soon after casting they do grow more with age.
I depend on it for a few boolits that are a shade small when cast and lubed. Others that are right to start and expand will show no difference when shot. Just need to chamber.
My .475" boolits cast at .476", go though a .476" die and will expand to .478" over time. They shoot the same.
Softer lead and smaller calibers expand less and pure doesn't expand.