I just had a minor breakthrough in reloading 9mm, and I thought my experience might benefit others. I realize that this will be old news to many of you, but here goes.
For months now I have been using expander plugs made by NOE Bullet Molds. For those who don't know, these plugs do the same thing that the Lyman M die does, but you use them with the Lee Universal Case Expanding Die. Anyway, these plugs solved my PC shaving problem, but created another problem for my 9mm loads, namely bulged cases. What I mean is that using them caused a very pronounced ring-shaped bulge in the middle of the case. I want to make it clear that this happened during the EXPANDING stage, NOT while seating the bullets. Using the Lee FCD removes most of the bulge, but some of it remains, and in extreme cases this will cause chambering issues.
After poking around on the Internet for a while, I discovered that some people were experiencing the same problem when using the Lyman M die. The problem arises from the fact that the brass walls of 9mm cases are a uniform thickness until you get about .220" down (by my rough measurement), at which point they get progressively thicker toward the base. You can clearly see this if you put calipers on the brass at the mouth of the case and then move them downward--it's easy going for almost 1/4", at which point you will suddenly encounter resistance. I was aware that 9mm cases are tapered, but I didn't realize this fact about wall thickness until yesterday.
The solution is to shorten the tip of the plug so that it doesn't hit the thicker part of the wall. A lathe (or an enormous drill chuck) would be handy, but I managed to do it using a bench grinder and a hand file. I put the plug back in the Lee die and voila--no more bulging! Another benefit is that my OAL is much more consistent. My brass is range pick-up, and I found that different brands would bulge different amounts. I would seat the bullets and then use the Lee FCD to iron out the bulge, which would increase the OAL by different amounts depending on the severity of the bulge.
As a side note, I've ordered a number of these plugs from NOE. If you look at the pistol plugs on their website, most of the sizes they offer have a long reach for the first stage, including all the sizes that are most useful for 9mm. I bought one that I use for .380 Auto that has a short reach, but I now realize that even that is a bit too long. .380 brass is straight-wall, but according to my calipers it exhibits the same wall thickening that I found with 9mm. My .380 brass also bulges, but not nearly as much as the 9mm did. Looks like I'll be firing up the bench grinder again....
Also, using a micrometer I found that the NOE plugs never measure exactly the same as the nominal dimensions. You can buy several of the same size and find up to .005" variation. I have one plug that measures about .003" small on the first stage and .003" large on the second stage. On the one hand this is bad, but on the other hand it can allow you to do some fine tuning if you have a large enough collection.
So, I just thought I would throw this out there in case anyone is having a similar issue. If it turns out I'm the last person on the planet to figure this out, please go easy on me!
John
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