Lee undersize die

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Lee Q. Loader

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I'm thinking about getting the Lee undersize die for 9mm. I have a bit of a problem with some brass headstamps in my Ruger carbine. They are Aguila, CBC and surprisingly, WIN. They won't plunk. Most all others with the same bullet and OAL are good to go. I can't figure out why.

From the research I've done, there is about a 50-50 chance this will solve my problem, so I'm willing to give it a try.
In the research I did about the undersizer, nobody mentions if it has an effect on accuracy. Has anyone noticed a change in accuracy using this die? Also if I switch to this die from the standard Lee die, do you think I need to work up my loads again? Maybe it will change the pressure?
 
I never had any issue with fitting a gauge or the barrel of a 1911 in 9mm but it solved my problem of bullet set back with some Federal and Winchester cases I had. I never noticed any difference in accuracy or any difference when shot past my LabRadar.
 
It doesn't sound like a sizing die problem, but maybe a crimping problem? Could be the brass you are having problems with may be shorter or thicker, thus your crimp die, adjusted for the other brass, is not taking enough of the flare off. If you were having setback issues or not having to flare the cases at all to start a bullet, then you would need the "U" die. I know, I had to get on for .380. But the tech at Lee admitted to me they had issues with setback with their standard .380 sizing die and even more so, with thin brass. The undersize "U" die is not going to make the overall size of the bullet+the thickness of the brass sidewall any different. Only impart more neck tension.
 
I started to use the undersized die when I got a new gun that had a much tighter barrel than my Glocks. I started with the undersized die and tested every round after loading with a size gage. Set the die to "touch" the shell holder. I also stopped using a crimp die and just set the setting die to crimp.
Bottom line for me is that it solved my problem with the gun, improved accuracy in both Glocks and the new gun.
 
Sure it is the brass? Have you tried the sized only cases
in a case gauge or your barrel before loading them?
Wilson 9MM Case Gauge Pic 1.JPG
 
Just as a FYI I have a Hornady 9mm die set and two Lee 9mm die sets.
Both the Lee dies (normal not undersized) size tighter than the Hornady.

I just bought a Ruger carbine (but haven't had a chance to load for it or even shoot it yet)
I have been wondering if shooting 9mm in the blowback carbine might cause sizing issue with the base of the case.
Guess I will find out shortly. (that is if I don't end up working on another of my weekends off.....)
 
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Blue68f100 said:
Does the sized only case fit your chamber? If so it's not the sizing. Could be your not starting the bullet straight, damaged rims .....
Click to expand...

Thank for all the help everyone. I haven't been able to try the sized cases in the barrel yet, but it's one of those, "Why didn't I think of that?" kind of moments. I'll try that and then I think, especially when I'm loading for the carbine I will start separating headstamps.
 
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Before you spend any money; whenever there is a fit problem measure! Measure the diameter and length of the offending cartridges and inspect the cases for any damage. Without facts (measurements) it's all a WAG...
 
This may be a little of base but are you seating round nose bullets with a flat nose seating stem in you seating die. If the profile on the stem doesn't match the profile of the bullet, round nose vs flat nose, the bullets may be seated a little crooked. This won't account for why the offending brass is only specific brands. But something is causing it.
If the bullets are seated a little crooked you should see a slight bulge around the side of the case in that area.
 
tightgroup tiger said:
If the bullets are seated a little crooked you should see a slight bulge around the side of the case in that area.
Click to expand...
Yep, more "bulge" on one side than the other, or no bulge on one side and a bulge on the other side.

Had a chance to check some sized brass only yet?
 
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We heck I never even knew Lee had a U die?? Been using Lee dies for a long time.

I have the Ruger PC carbine and shot all kinds of headstamps through it using the regular die along with the dreaded FCD:)
As well as match barrel pistols.
 
After reading all about how Lee dies size 9mm better, I just ordered one to add to my Redding 9mm Pro Set. Using my Midway birthday discount, I figured I might as well go ahead and order the undersized die.

The set will look a bit odd with the Lee Sizer, Lyman M Expander, Redding Competition Seater and Crimp die...my RCBS and Hornady 9mm die sets are going to be jealous
 
My RCBS dies do a good job resizing my 9mm brass. In my mixed brass groups I'm not even careful about what kind of brass is in there, I sort mine but I'm looking for ammo-land and other junk like that.
My mixed brass is a hodge-podge of about anything that hits the range floor and I check my neck tension on all the brands with my strain gauge so I know I'm getting 35lbs of tension and up with that mix.
I always thought RCBS sizing dies made really good neck tension and you get both seating stems to boot, one round nose and one for flat nose, when you buy their carbide pistol die sets.
That's a win-win for me.
Lee resizing dies are also good in that, like RCBS, they will size down further on the case then Hornady dies will. I think I read somewhere that Hornady dies are more beveled on the bottom of the sizing ring to help the cases start in the resizing die better on their progressive press. Lee, RCBS, and Redding dies aren't beveled as much.
In a case like .357mag that doesn't mean as much as it does in a 9mm.
With 9mm and other similar style cases, it could be a big deal, you want that sizing ring to go as far down on the case as possible.
I think Lee dies do that better than any of them, the carbide ring is pretty much the lowest thing you see on the bottom of the die, but it leaves the carbide ring vulnerable to ram damage, (cracking the ring) in a single stage presses.
Progressive presses have some flex in the shell plate and that helps keep them from damage from hitting the shell plate where single stage presses do not.
If your careful when you set the Lee die up in a single stage you will never break one.
But accidents do happen.
 
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Lee Q. Reloader wrote:
I'm thinking about getting the Lee undersize die for 9mm.
Click to expand...

Why?

I have used a Lee Full-size 9mm die for years without any problem.

Before buying a new die, try looking first at how your current dies are adjusted. My bet is that you don't have the dies you already own adjusted properly.
 
Walkalong said:
Yep, more "bulge" on one side than the other, or no bulge on one side and a bulge on the other side.

Had a chance to check some sized brass only yet?
Click to expand...
Ok, the sized brass plunks just fine....all headstamps.
As many have responded, I now need to see if crimp with these headstamps is the problem or crooked bullet seating. Regardless I'm going to always separate headstamps now and adjust dies for each.
Probably need more flaring and proper adjustment of crimp die.
Thanks everyone for saving me the cost of the undersize die. I'll use the savings to buy more powder!
 
Glad you located the source of the problem.

When I started 40+ yrs ago you had to figure things out on your own, fellow reloaders (if you knew any), and old fashion books. No internet back then, information was hard to come by. This exercise will make you a better hand loader. There is most always a reason something does not work. Why some jump on the LFCD to fix there problem with out researching the cause. I still do not own a LFCD. School of hard knocks have taught me to keep digging till I find the root of the problem.
 
FWIW I just adjust my 9MM dies to taper crimp the thickest walled brass to work in everything and load em all up. In the beginning I tried to crimp each brass type differently to get max accuracy. Then one day I forgot to adjust the seating die and guess what! I could see no accuracy difference so now I just leave it set for the thickest ones and load on. YMMV
 
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