.357 Mag Bullet Sizing

[Ridge & Valley]

Greetings all! Newish caster here. I have several hundred Lee TL 358-158 SWC bullets that I cast and powder coated for use in .357 Mag. As is, their diameters vary from .359" to .362". I bought a Lee bullet sizer in .357", figuring I'd use gas checks with these, but the Hornady 35 cal checks don't fit the base. (They just get mashed.)

Will I have issue with these at .357" without checks? Should I buy a .358" or .359" bullet sizing die? Alternatively, would the un-sized bullets be safe to shoot at the upper .362" diameter? Thanks!

[toallmy]

What mold did you cast your boollits with ? If the boollits do not have a gas check shank you can't put a ( standard gas check ) on it , but some people use a ( plan base gas check ) on boollits designed without a gas check shank .

[Dusty Bannister]

The Lee TL bullet you have selected does [NOT] have a reduced base band (gas check heel) to accept a gas check. When you powder coated first, it will make the heel too fat to allow fitting on the gas check. If the powder coated cast bullet will barely slide through the cylinder throat, it can usually be safely loaded. Start with one of the bullets that mic largest diameter of .359" That might be too large to pass through without heavy force. If it does not press through with slight pressure, you are better off to size to a smaller diameter. You are going to find that .357" is probably going to be too small and gas cutting when fired is going to result in leading in the barrel.

In your case, please start with the suggested starting load in the cast bullet manual and slowly increase the powder charge to an acceptable accuracy level or the max load is reached. You seldom need a max load for good accuracy.

[Walks]

If you're having hard sizing, you might think about a bit of lube to aid in sizing. One of the case sizing spray lube or even Pam cooking spray. Just a bit over the bullets in a shallow bowl, swirl them around and wait 5 minutes then try sizing.

[tazman]

My usual sizing for 357mag is .358. It seems to be the accepted standard.
As others have said, if the boolits will form a tight sliding fit with the cylinder throats on your revolver, they will be fine at that size. Some people will shoot them even tighter but the best accuracy seems to come from a tight sliding fit.

You haven't mentioned what firearm you are going to use these in. Everyone here will assume a revolver unless you state specifically for a rifle.
Every revolver has it's own dimensions. Even the most consistent manufacturer uses tolerances and may have slightly different cylinder throat sizes.
We can make educated recommendations but your specific gun has the final word in what works.

[robg]

i size to '358 with lee push through sizer only with gc boolits .plain base i shoot unsized.

[mdi]

When you're talking about cast bullet sizes, you need to know a couple things; throat diameter (measured with pin/plug gauged, expanding ball gauges or slugged) and barrel groove diameter (slugging is easiest). When measuring slugs use a micrometer and measure several slugs. "Drop through", "push through", "tight and loose" are not measurements and not much better than a WAG. Nekkid, High-Tek or PCed bullets are best sized to the same diameter as the cylinder throats. The cylinder throats are/should be larger in diameter than the groove diameter, so a bullet the same diameter as the throats will be a good fit. No guessing. Usually just done once per gun.

This method has worked quite well for me for sizing my cast for 10 revolvers for the last 30 or so years. Fit is King!

[JonB_in_Glencoe]

Ridge & Valley,
welcome to the forum.
You don't need GCs for 357 pistol loads.
as to the .362 boolits, load 'em up, if the finished round fits in the chamber, you are good to go...Shoot 'em up.

[fredj338]

IMO, 0.358" is minimum size. Check your cyl throats by pushing a 0.358" lead bullet thru. If it wont go thru easily, your throats are probably too tight & will size any bullet to that dia.

[gwpercle]

The Lee TL358-158-SWC is NOT designed to have a gas check placed on it . It is a Plain Base design (PB) . The TL means Tumble Lube . C358-158-SWC is the one designed for a Gas Check . Lee puts a C in front of the number to indicate Check .
But that's okay ...hang onto the gas checks you will be buying more moulds ... trust me , they get to be habit forming !
Powder Coat them and try to get a thin even coating ... you can size them to .357" or .358" .
Since you have .357" try that first ... sizing to .358" is just easier... my thoughts are size them as little as required .
You have a lot more leeway with revolver , 38 special / 357 magnum , and sizing ...semi-auto handguns and powder coated sometimes get to "fat in the ogive and give you chambering problems ,
no problems with revolvers ! In all my 38 Special and 357 Magnums both S&W and Ruger ... it doesn't seem to matter if I size my boolits .357" or .358" . I did an extensive test and my revolvers don't show much if any difference at 25 yards ...the distance of my nearest indoor range . I sized them .357" for 40 years because the Lyman Manual said to , learned here .358" was better , I was honestly expecting a big improvement ! But it didn't seem to matter some I size .357" & others I size .358" it all depends on what size the cast boolit drops from the mould.

And let me add ... Welcome To The Addiction !
First round is on me
Gary

[Cosmic_Charlie]

I size to .357 with several of my S & W revolvers. Because that is the size of their cylinder throats. Letting the throats size your boolits down is less than ideal. I use medium loads with softer alloy, both powder coated and conventional lube. Try some at .357.....