Why would I want an undersized 9mm die?

[TheGerman]

Was browsing and came across a 9mm Lee die that is .003 undersized from the factory.

Why would you want/need this? Something to do with the Lee die specifically in that the 'stock' one from the factory sizes too big by default? Or is this a pistol specific thing people do?

Pistol Undersize Carbide Sizing Dies

Lee Precision, the nation's number one manufacturer of reloading equipment for over 50 years presents its full inventory of quality products.

leeprecision.com

 

[fxdrider]

Was browsing and came across a 9mm Lee die that is .003 undersized from the factory.

Why would you want/need this? Something to do with the Lee die specifically in that the 'stock' one from the factory sizes too big by default? Or is this a pistol specific thing people do?

Pistol Undersize Carbide Sizing Dies

Lee Precision, the nation's number one manufacturer of reloading equipment for over 50 years presents its full inventory of quality products.

leeprecision.com

I went to the Lee website to their "Undersize Sizing Die" page, and they're all handgun calibers - mostly semi-auto.
I did a search and found on another forum someone asked the same question. Seems it's for those who reload range pickup brass. It's a way to make damn sure the round chambers reliably. Not sure why the normal-sized sizing die wouldn't do that either.

 

[_Windrider_]

Cause your poor and can’t afford a full size?

 

[TheGerman]

Cause your poor and can’t afford a full size?

/sadpanda

 

[kriller134]

I’d imagine it’s like a small based die. Probably to help with brass that’s been fired out of an unsupported chamber.

 

[Threadcutter308]

Ever measure the inconsistency of OAL of range pick up brass ?
PITA when you’re trying to apply a slight taper crimp on reloads.....

 

[TheGerman]

Ever measure the inconsistency of OAL of range pick up brass ?
PITA when you’re trying to apply a slight taper crimp on reloads.....

So Im guessing this ended up being a good question.

The literal shit ton of 9mm brass I've scammed my way into is all brass, but from probably a million different pistols.

Get the undersized die then?

 

[Threadcutter308]

So Im guessing this ended up being a good question.

probably, yes. Although, it won’t do anything for OAL variations.
(flame suit on)

 

[Powder_Burns]

Maybe for a tighter match chamber?

 

[NCHillbilly]

So Im guessing this ended up being a good question.

The literal shit ton of 9mm brass I've scammed my way into is all brass, but from probably a million different pistols.

Get the undersized die then?

I've loaded and shot tons of 9mm for years, most loaded in range pick-up brass, and have always used a standard RCBS carbide sizing die with no issues.

 

[Milo 2.5]

So Im guessing this ended up being a good question.

The literal shit ton of 9mm brass I've scammed my way into is all brass, but from probably a million different pistols.

Get the undersized die then?

If you have that much brass, maybe a roll sizer is an option.

 

[Adam B]

In uspsa it is the best way to guarantee that you ammo will pass a case gauge and chamber in your gun with no issue. I run them in 9 and 40.

 

[918v]

Because Lee’s regular sizing die sizes minimally, almost like its neck sizing. A lot of people don’t like that.

 

[Carolina Hill Billy]

I’ve used the 9mm and 40 U dies for thousands of rounds. I bought one because my bulk loaded rounds wouldn’t always fall free from the case gauge. I’m not sure it’s always needed but it doesn’t seem to hurt anything. Everything goes in and out of the gauge much easier so I’m guessing it could decrease jams in borderline ammo?

 

[Winningdog]

I’ve used the 9mm and 40 U dies for thousands of rounds. I bought one because my bulk loaded rounds wouldn’t always fall free from the case gauge. I’m not sure it’s always needed but it doesn’t seem to hurt anything. Everything goes in and out of the gauge much easier so I’m guessing it could decrease jams in borderline ammo?

How much does it effect bullet seating or pressure. Did you need to change amount of powder?

 

[Powder_Burns]

Its 9mm. Don’t overthink it.

 

[Carolina Hill Billy]

How much does it effect bullet seating or pressure. Did you need to change amount of powder?

I didn’t make any other changes. The seating pressure seems normal. It gives a bit more grip to lead bullets in 357, I think. But nothing you’d need to compensate for.

 

[padom]

Ive sized 10's of thousands of 1x mixed headstamp 9mm brass sourced from online individuals, local people selling and range pickup by the 5 gallon bucket full. All my 9mm sizing is done on a Dillon XL650 using Dillon carbide 9mm sizing die. Every single round drops into a 9mm case gauge perfectly and Ive never had an issue chambering or firing any of my 9mm loaded rounds. The Dillon 9mm carbide dies just plain work..

 

[Steel head]

It was an old fix for the dreaded glock bulge?

 

[buffybuster]

Some guys are running Major9 and/or custom minimum spec chambers. Those benefit from an small base die. If you have a factory chamber then it's no benefit. It won't hurt, just doesn't help.

 

[Powder_Burns]

If you run a Lee FCD it will resize the case for you while setting your taper crimp. Potential chambering issues solved.

 

[918v]

If you run a Lee FCD it will resize the case for you while setting your taper crimp. Potential chambering issues solved.

FCD won’t size the bottom of the case anymore than the regular sizing die will.

 

[redleg1013]

Firstly, it's something you'll see the pistol gamers use, kind of like a small base die for pistols to make sure that every round chambers. They are radiused to size further down the case to eliminate deformation caused by unsupported chambers, like Glock, specifically 40 S&W. They also get used a lot for range pickup brass just so it all starts on an even field when reloading. One piece from the school of lessons learned, it kind of defeats the purpose to use a U die and load lead, you're just gonna wind up shaving EVERY round. It's a good band-aid if you have a tight chamber (or one that wasn't finish reamed) and plan on higher volumes of firing.

 

[918v]

A “U” die doesn’t shave lead. It sizes the bottom of the case more than a standard die does, not the top. If you’re shaving lead then you didn’t bell the case mouth enough, or the bullet is too big for the seater die bore.

 

[Bullspotter]

All my pistol brass was range pickup or bought as once fired, 10,000s of thousands, 9mm and 40, Never had any issues case gauging 9mm loaded with a dillon carbide, same with 40 loaded with a RCBS carbide. Had issues with .40 in some of my guns setting the bullet back when chambering a round. 2 limited 2011s and one 1911, so i use a U die for loading for those, problem solved .40 in glock and XDs are fine with regular sizing (RCBS).

 

[Bullspotter]

A “U” die doesn’t shave lead. It sizes the bottom of the case more than a standard die does, not the top. If you’re shaving lead then you didn’t bell the case mouth enough, or the bullet is too big for the seater die bore.

my .40 U Die absolutely dose size the case mouth smaller then my RCBS carbide die dose.

 

[whatsupdoc]

My lee 9mm die puts the case neck at .373 and .200 from the base is .388, there is no SAAMI chamber that will not
accept sized cases from this die.

The lee undersize die most likely was designed to resize problem brass possibly Glock smiley face or SMG brass.

 

[918v]

my .40 U Die absolutely dose size the case mouth smaller then my RCBS carbide die dose.

Apples to oranges. Different brand dies size different.

 

[Swatman]

Basically you use them to make sure every round will chamber without having to case gauge. You may also be able to get an extra round or two in the magazine with 9 or 38 super comp. You don’t need it to rehab range brass. If the brass is that bad you can roll size or use a push through base sizing die. I shoot a lot of pistol and have never needed to use anything like those tools.

I tried one in 38 supercomp and it pretty much stopped my Mark 7 because of the extra torque needed to size. Also they aren’t beveled like other dies so you get a lot of damaged brass if the shell plate doesn’t align perfectly by the time the dies come down.

I think it answers a question that no one needed to ask. Definitely not worth the hassle.

 

[Mike Casselton]

I’d imagine it’s like a small based die. Probably to help with brass that’s been fired out of an unsupported chamber.

Range pickup and the Glock chamber.

 

[pmclaine]

"Undersized 9mm"

Do you tautology much?

 

[smoothy8500]

No, but I do pontificate on the benefits of small-base dies...

 

[pmclaine]

Ive sized 10's of thousands of 1x mixed headstamp 9mm brass sourced from online individuals, local people selling and range pickup by the 5 gallon bucket full. All my 9mm sizing is done on a Dillon XL650 using Dillon carbide 9mm sizing die. Every single round drops into a 9mm case gauge perfectly and Ive never had an issue chambering or firing any of my 9mm loaded rounds. The Dillon 9mm carbide dies just plain work..

I think Dillon cuts their dies TIGHT.

Generally not a bad thing, certainly not a problem with pistol and I get plenty of reloads in rifle.

The rifle dies though really squeeze necks and a neck sizing mandrel becomes your friend.

@TheGerman see if you can get a set of lovingly used 9mm dies here....Ibet there are some in the PX now. Dillon was built around feeding subguns and other MGs and I think they built their dies to suit.

 

[Tchitcherine]

I loaded a shit ton of rando range brass, using the standard Dillon carbide die set.
Recommend start searching for a solution if you have a problem, not the other way around.

 

[NighthawkCG]

Just bought a LEE U die a while ago to start my 9mm reloading. Have gotten great results out of it. Haven't loaded lead, but no problem with jacketed or plated. All of my brass was range pickup.

Like said above, not sure it would hurt to use the U die. I was having trouble finding dies at a reasonable price and the U was all that was available. No regrets here and I have run the loads easily through pistol and PCC.

 

[RMH in AZ]

I am a bit OCD so I sort all of my pistol brass by head stamp. For my 9mm I use Lee dies. I found that FC brass has a thinner wall thickness so couldn't get the neck tension that I could get with Winchester brass.

What I found was that the sizing die I have is a bit on the large side. Rather than contacting Lee with the the issue, I just bought the U die for the F C brass. My original one works great with all other head stamps.

 

[Zatchmo]

Holy back from the dead thread.

A lot of uspsa guys use them for extra insurance against bullet setback. Open guns are violent. I used to have issues around the 3-4th reload with bullet setback. 38 super comp brass is expensive. A $40 u-die and I can shoot it until I lose it.