Lee 9mm decap die marked with U

[Alvarez Kelly]

I recently bought a lot of mixed dies. Included was a Lee 9mm carbide sizing/decap die. It has a random U stamped on one of the wrench flats. Anyone know if this is the infamous Lee U die? Their website says the undersized die is 3 thousands smaller.

[Alvarez Kelly]

Well... I kept digging online. I found a youtube video of a Lee U die. Sure enough, it had a big U stamped on the side. Still, I figured someone here might have more experience with the Lee undersized die.

[onelight]

Be easy enough to check if you have a standard 9mm die.

[Alvarez Kelly]

Be easy enough to check if you have a standard 9mm die.

I don't reload 9mm, so no. Its not easy for ME to check.

[JimB..]

It’s an undersized die, I have several that I got from an estate. Haven’t ever used any of them.

[Carrier]

Yup that would be it. I used when I loaded 9mm.

[Alvarez Kelly]

Thanks for the confirmation Gents. I figured someone here would know.

[swmass]

It’s an undersized sizing die. I have been using them for a few years. I was having an issue with 38 special and 45acp brass a few years back. When I would size with the normal die, the bullet would have no tension and could easily be pushed into the case by hand. Typically a problem with Remington or thinner brass. The U die gets rid of that problem and allows me to
use mixed brass and ensure there is proper tension on the bullet. Some of the most accurate hand loads I have produced have been with this die. You should have no problems with it.

[usbp379]

https://www.egwguns.com/undersize-reloading-die-9mm-luger

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[mdi]

Just wondering, every problem I've ever had I have been able to work out without resorting to "special" dies. For my 9mm handloads, since 1998, I have often used mixed brass, range pick ups (every kind sold in my area and a few that I've never heard of). I have never had a problem with loose neck tension with several jacketed bullets from 115 to 147 gr, cast lead to .358", plated at .356", PCed and Hi-tek coated at ,356"-.357", and some European military pulls, in any brass I use. I only have 3, 9mm pistols, two of modern American manufacture and one older Tokerev, and every handload I've produced will feed, chamber, fire with zero problems as long as I do the plunk test checking workable OAL. So if one used decent components, why would an undersize die be needed?

Edit on Sunday; not a challenge, or questioning anyone, just want to know. I understand a U die makes the case smaller in diameter, but why? In my experience (above) I have never had the need, or come close to need an undersize case sizing die...