Sizing .40 S&W with Lee sizing die

[ranger391xt]

I have searched and found some statements in other threads about Lee size dies sizing cases smaller than spec. I have noticed this happening with my .40 S&W case mouth being sized down to .418", which to me is quite a bit below the .423" spec.

I was wondering if this is what others see when sizing .40 S&W with a Lee sizer or if perhaps one of Lee's "undersize" dies made it into the 4 die pistol set I have.



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[Jniedbalski]

I guess it depends what thickness the cases are. Some are thicker than others. .418 to .423 is only .005 . .0025 on each side of the case. Most all reloading dies are made jacked bullets so they usally size a little to small for cast bullets. That’s why I got the noe expander for 9mm and 40 S&w my lee 40 die with the lee universal expander tool and noe expanders work great

[44magLeo]

That .423 spec is for a loaded round. You have to size it smaller to grip the new bullet.
Most any sizing die will size the cases smaller than the loaded spec. They have to. Brass comes in varying thickness. Some have thin walls, some thick, The sizing die is designed to size even thin cases enough.
Now in the second die you use it expands the brass up to an internal diameter that is a couple thou under bullet size.
Measure your cases after you run it through the expander die. What size are they?
Seat a bullet into the case, What size is it now?
Report back the measurements you find at these stages.
When this brass was loaded rounds did you measure them then? Do you have any of them to measure?
If you measure loaded rounds I doubt you will get that spec. It will be close.
Try a different brand and measure. You might find it bigger or smaller.
Not all brass comes out exactly the same. Even from lot to lot on the same brand.
That spec has a + or - tolerance. So even if your reloads don't exactly come out .423 it will be ok.
On an auto the that uses a straight case like your 40 does, there is a step in the chamber that stop the cartridge
from going to deep in the chamber. The end of the case hits this step. As long as your cartridge drops into the chamber and stops on this step your fine.
The step is from just over bullet diameter on the inside edge to just a bit over that spec you have on the outside edge.
This lets thin brass hit this step and lets even the thickest brass into the chamber.
Hope this helps.
Leo

[MT Chambers]

The Lee dies are just for the first sizing of the case, then you need a proper sizing die to size/expand the case.

[country gent]

As stated above most dies size undersized to accommodate variations in neck wall thickness then expand back up to size with the proper tension for the bullets. Usually .002 on dia. This is normal with most dies. With pistol dies now ( as most are carbide ) It is harder to work them out larger in size.

A die can be reworked to size just what you want it to. The lapping can be done with sized cases or a mandrel and fine sand paper then polished with a flannel patch and fine compound. The plusses are brass sizes easier, brass lasts longer, and may bee a slightly better fit in your chamber. Draw backs are some brass may not size down enough do to thinner necks, Brass may not fit chamber being tight. The thing to remember here is once material is removed it cant be put back easily. If you good with a lathe a die can be converted to neck bushings making it adjustable for different brass and or tensions.

To simply polish the die out. split a piece of 1/4" aluminum rod down 1/2"-3/4" from one end. Cut a piece of 600 grit 1/2" wide and wrap to a snug fit in the die and carefully insert into die . turn slowly in a drill motor working back and forth . work slow and clean and size cases often checking size often. A few drops of light oil helps a lot. The carbide ring is very hard and abrasion resistant ( 70-80 rc) the die body is softer and will cut faster. get close and then a 1/2" strip of flannel with polishing compound to give the fine finish you want. The die body may be case hardened or fully hardened and in the 45-60 rc range.

[ranger391xt]

Thanks for the replies. I asked becuase the difference in diamteter at the mouth vs the head was pretty noticible after sizing and the finished rounds have a bit if an "hourglass" look to them. I have no issues chambering rounds I've made. I guess i was more concerned about working the brass too much.

@44MagLeo, I took some measurements and here are the results.

After Sizing
Mouth: 0.416"
Body: 0.418"
Head/Web: 0.422"

After Expanding:
Mouth: 0.434"
Body: 0.418"
Head/Web: 0.422"

Conplete Round:
Mouth: 0.4225"
Body: 0.418"
Head/Web: 0.422"

Thanks again for the responses.




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[David2011]

A certain amount of brass working is unavoidable. Pretty much every failure of .40 brass I’ve had was in the sidewall below the mouth. Maybe all of them were below the mouth and I’ve shot a lot of .40. I really can’t recall a split at the mouth. It’s not uncommon to see the hourglass that you describe. As long as you’re not sizing the boolits down when seating them and the rounds chamber without fail you’ve done all you can. I’ve loaded almost 100,000 rounds of .40 at this point.

[44magLeo]

To eliminate the hour glass shape I might try backing the sizer die out enough so you are only sizing the case as deep as the boolit is seated.
Kinda like neck sizing a bottleneck case.
I do that with most of my straight walled cases.
I don't have an auto, and neck sizing my not work well. It may leave the case a bit tight and fail to chamber. A bit of experimenting will determine if it works.
Neck sizing straight wall cases has all the benefits of neck sizing bottle neck cases.
Your cases get fire formed to a perfect fit in the chamber, why make them too small again. Over works the brass. Shortens case life.
Again with an auto or a revolver for carry purposes or competition full length sizing may be the best way to ensure positive chambering.
Losing a competition from a jam sucks, so does loosing your life.
On your measurements, they look about as I expected. Size a bit small, then expand to the right size.
On the case mouth size after expansion you list .434, I assume that's with a bit of bell to ease cast boolit seating. It help with J-word bullets too.
So it sounds like they are working ok.
Leo

[W.R.Buchanan]

I can't believe that what is going on here isn't common knowledge by now as it has been discussed many times in the last 10 years.

There are threads on this.

Since I don't have anything else to do I will go thru it again.

First: in order to remove the bulge on these cases you shove them all the way thru a Lee Deluxe Factory Taper Crimp Die with the carbide ring and the Taper Crimp Ring removed. This will return the entire case to about .421-.423. OD.

You do NOT use the Full Length Sizing Die for this "Case Prep" Operation as the case head will not go thru the sizing ring of the die! (You can't Compress Brass)

After this step is done, you Reload the cases normally starting with the F/L Sizing/Decapping Die. Then the Expander/Charging Die, then the Bullet Seating Die, then the Factory Crimp Die with the Taper Crimping Ring reinstalled and adjusted until the crimped round measures .417-.418 at the case mouth.

Done! simple as that.

Randy