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Thompsoncustom
07-09-2013, 02:44 PM
I've been having some undersizing problems lately after I turned down my lee expander plug which is no big deal as that gave me a good reason to buy an M die. So M die came in today and I loaded 40 rounds and decided I better pull one just to make sure it's not undersized. Before I loaded the bullet is measured .3565 and after I pulled it .351

What the heck is going on. Seems like no matter what I do these days all my bullets are undersized by the case. This is how my reloading has been going. On the Hornady LNL I resize and deprime and reprime the case, after that is all done I set up the Lyman M die is station one, LNL powder drop in station two, Three empty, 4 lee seating die, and 5 empty.

After I found out they were being undersized I back off all crimp completely and tired again but that made to difference.

The bullets are lee 125gr WW that are air dropped. Could the lead be to soft? I would think you could run pure lead so I don't think that's the issues but at this point im lost.
tyeo098
07-09-2013, 03:46 PM
Measure the expander plug.
Thompsoncustom
07-09-2013, 04:16 PM
.3535 according to my calipers. Seems small what is the norm? .355?

Edit: Just realized I used two different calipers to measure the bullet and the stem.

On the new calipers the bullet is .355 and the stem is .3535
runfiverun
07-09-2013, 08:27 PM
and then add shrink back on the case.
measure the inside of the sized and opened case.
MtGun44
07-09-2013, 09:17 PM
Micrometer time.

Bill
Thompsoncustom
07-09-2013, 09:32 PM
Micrometer time.

So true....

Anyone put a .357 or 38S&W expander plug in the M die for cast 9mm? Or does anyone have either of these plugs they could measure? I think I need to expand some more but want to have keep good neck tension.
fecmech
07-10-2013, 09:55 AM
The 38P "M" plug for .38/.357 measures .356" on mine.
mpmarty
07-10-2013, 10:11 AM
Which die do you crimp with? If it's a LEE that is your problem.
Thompsoncustom
07-10-2013, 07:56 PM
The 38P "M" plug for .38/.357 measures .356" on mine.

Thanks I ordered two of them today might turn one down to .355 if I don't have enough neck tension.


Which die do you crimp with? If it's a LEE that is your problem.
Your saying I shouldn't be adding crimp with my seating die? I backed it completely off and it didn't seem to make a difference.
mpmarty
07-10-2013, 08:20 PM
Your saying I shouldn't be adding crimp with my seating die? I backed it completely off and it didn't seem to make a difference.

No, I mean that the LEE so called factory crimp die for pistols is famous for sizing boolits down when used at all without regard to "how much" you crimp. It has a carbide ring at the entrance that sized down both the brass and lead going in and coming out.
Thompsoncustom
07-10-2013, 09:34 PM
Guess I should have put that in bold. No I don't use the FCD tho I still have it, it doesn't see the light of day.