Explain sizing requirements, is there a chart or sticky?

[bgiff]

I bought a lee sizing die because I thought I had to size my .358 Lee 158 grain bullets. But the die just destroys them. My mold says .358, the sizing die says it's .357. What am I doing wrong?

I fired a couple un lubed, un sized 158 gr bullets and they seemed to work fine.

[35 Rem]

Is your mold for a Tumble Lube bullet? I suspect that's the case. The end of the part number on those has a "TL" on it. They are intended to be shot as cast with some kind of liquid lube applied and no sizing. After the lube has dried, usually over night, a Tumble lube bullet is loaded without any further processing. I am trying to recall but I don't think I've ever tried to size a TL bullet. I'm guess it would smear up the tops of the round grooves and that may be what you are referring to? A .357 sizer is most likely too small for any 38 Special of 357 Mag anyway. The usual nominal is to go one thousandth over normal jacketed bullet diameter for sizing of a lead bullet. The best way is to actually measure the gun 1st then buy a sizer based on that value.

[C.F.Plinker]

Please post pictures of your mold, sizing die, unsized boolet, and sized booklet so we can see what is happening.

[vagrantviking]

If they chamber and fire fine unsized you can go that way but you will want tolube in some fashion. Tumble lube with Lee Alox is very easy-to-use.

For help with the sizing, you will need to provide more information as mentioned.

[JonB_in_Glencoe]

bgiff,
welcome to the forum.
For 357 mag?
"is there a chart or sticky"
Your gun will tell you what size.
I size them to .359 for my Ruger GP-100.

.357 is probably a bit small for most 357 mag guns, but you need to measure the throats to be sure.

[mehavey]

my .358 Lee 158 grain bullets

Please, which actual mold ?
- 358-158 RF ?
- TL358-158-2R ?

[fredj338]

As cast bullets can be any size +/- of the mold. Alloy & temp give you a final size. Your bullet sizing die may be 0.358 or +/-0.0005". If you want to size the bullets t00.358", then that is the die size you need, no 0.357".
When you say the die destroys the bullet, what exactly do you mean?

[243winxb]

Lube bullets before & after sizing, using Lee Alox method.

https://support.leeprecision.net/en/knowledgebase

Tips and tricks from LEE.

The higher antimony content in the alloy, the larger the sized bullets will be.

A .357" die can produce a larger diameter, measure after sizing. Spring back.

[Bazoo]

bgiff, welcome to the cb.gl forum.

Can you elaborate on how the sizing die destroyed your bullets?

You cannot fire lead bullets without some kind of lube and not get severe leading. You can fire them, and in fact, it was once suggested to fire a cylinder full as a learning experience to witness what severe leading in the bore looked like.

You do not have to size bullets, provided they fit your chambers after being loaded into the cases. People often times do not size Lee bullets, and merely just tumble lube them. This presents a problem occasionally if you have a fat bullet in the mix, which will then not chamber.

It's a good rule of thumb to start sizing 38 Special and 357 Magnum ammo at .358. If the groove diameter of your bore is under .357, you can get away with that too.

Most of the time, a larger bullet is more accurate because it fits the cylinder throats better. But that doesn't mean you have to size to fit the cylinder throats to make decent, functional, and even accurate ammo. It might mean the different between 2" groups and 1 ragged hole at 25 yards, but 2" groups are fine for plinking and field work. You can always change your procedures later on if you find that you need to.

[stubshaft]

Buy a good caliper and measure the cast bullet then slug the bore and measure the slu. Without any measurements you have NO WAY of knowing where you are.

[dondiego]

Buy a good 1 inch micrometer.

[HamGunner]

The cartridge designation (.357 Mag) was only that, a designation and not really a reference to the actual bullet size. Some use the .357 sizing die to size 9mm bullets if their chambers allow. Of course, the 9mm bores are smaller than .38 Special/.357 Mag.

In most of my revolvers, I would rather size my .357 Mag bullets to .359 if the chamber throats and or brass thickness allows, certainly at least .358 dia., but then one needs to know the bore size as well as the cylinder throat size first in order to know what is needed in your gun.

Normally, what you are shooting for as to bullet size is that of the cylinder throats. If the bore is no larger than the throats you are good to go. If the bore is larger than the throats, then your throats will always be feeding the barrel undersized bullets. Not as much a problem with jacketed bullets as they are more tolerant to gas blow by, but with cast or swagged lead bullets, it certainly is a problem.

Yes, I certainly agree with others. Any handloader needs a good caliper, but they certainly need an even better micrometer.

[BJung]

A handgun barrel slugged at say .357 will use a .358 sizer die or maybe even .359. The .357 sizer is for 9mm that could slug at .355-.356". The simplest way to size your bore is to find a fisherman and ask for a sinker that's close to the bore. Grease that and drive the "lead" sinker through the bore with a wood dowel that's just under the bore size. As mentioned, use a micrometer to measure the diameter of this swaged lead, add .001" and that is the starting size of your bullets. I hope this helps.

[dondiego]

Many mishaps have occurred using wooden dowels to drive slugs through the bore. Use a brass rod.

[DougGuy]

Buy a good 1 inch micrometer.

+1! Forget starting with a caliper, it can easily introduce errors that a mic normally would spare you from. Buy a quality 0" - 1" micrometer with a friction thimble and a digit readout like the Mitutoyo 193-211. Buy a micrometer stand too! worth their weight in gold when you can use one hand to hold the boolit and turn it, move it up and down between the anvils, operate the mic with the other hand.