9mm loading help

[divingin]

The M die expands the brass where the bullet is seated to avoid inadvertent sizing of cast bullets. It is supposed to allow for minimal interference fit between bullet and brass, but still semi-support the bullet at the base where the expansion stops. The "flare" is accomplished by a step in the expander, which should open the brass up a bit more at the mouth, allowing a bullet placed on the mouth to sit slightly in the case (which prevents it falling over or out.) The flare is removed at the crimp step (Since it's not a flare, per se, but a stepped expansion, IMO a taper crimp would be a better choice than a roll crimp.)

The NOE plugs are basically custom sized M die plugs. They work well, assuming you figure out what size you need. They're ID'd by expander diameter, flare diameter, and depth of expansion, as I recall. When I was ordering one for 32SWL, I chose a thousandth under bullet diameter, didn't care about flare diameter, and chose just short of bullet length. Worked out pretty well, though I think going for full bullet length may have been better (I was loading flush wadcutters. For any protruding bullet you could adjust seating depth.)

Ideal plug size will be different between jacketed and lead bullets, as lead is generally run a thousandth larger (and lead is more susceptible to being sized down due to interference fit.) Not to say you can't run the same size, just that ideally they'll be different.

Measuring with digital calipers I get .376 using the lee expander and .379/.38 using the lyman. Just want to be sure with the larger diameter I won't get a round stuck in the barrel. I did load 5 dummy rounds and they seemed to cycle fine manually.

Best way to tell is to pull the barrel and drop the cartridges manually into the chamber. They should fall fully in with no resistance, though a slight drag will probably work as well. If they have to pushed in with any kind of force, you'll eventually have problems as the chamber accumulated stuff from firing.

[bigbossman]

I clicked the link and had no idea what I was looking at. How do I determine the correct size?

I was unsure when I looked at the webpage, so I just called and talked to the guy that makes them. Who knows, might work for you too.

you do not flare the mouth wide enough. Adjust the lee sizing die a tad lower and it will flare the mouth open a bit more. I adjust it just enough so the bullet sits in the case. When you seat the round it should push it in and not really expand it any more that it needs to just seat the around. I then do a slight crimp.

This is the answer, for a Lee die. Just screw the die down a bit at a time to get the desired flare. No need to buy a Lyman M die. Besides, Isn't the M die designed for rifle brass? I doubt it will work on a 9mm, but maybe I'm wrong.

Also - the expander die doesn't determine the final diameter of the case mouth, the taper crimp die does. You can expand the case mouth a considerable amount, and the final taper crimp operation will set the diameter to the proper dimension.

[divingin]

You can expand the case mouth a considerable amount, and the final taper crimp operation will set the diameter to the proper dimension.

You can, but you'll also get split case mouths pretty quickly. I try to work the brass as little as possible to avoid that.

One advantage of the M die (or similar expander made by others) is that the flare portion is not simply formed by a conical section - it's actually a slightly larger step that forms a cylindrical, slightly larger opening at the mouth. The bullet slips into this section like nesting tent poles and doesn't tend to tip out.

As to M-dies being for rifle only, there's this:

https://www.lymanproducts.com/pistol-neck-expanding-m-dies

[tawadc95]

I love my type m's, great die.
My 9mm's are set to .378-.380, this fits my 2 Shields and 2.0 barrels just fine. How they fit your chambers is the important part not so much the finished diameter within reason of course.
If in doubt set your crimp die up to the measurement of a factory ammo your gun likes.

[rdtompki]

The Mr. Bullet Feeder expander is very highly regarded. I've used one for in excess of 150K rounds, initially on an LnL and currently on a 1050 with an autodrive. If the expanded case can hold a bullet at 1800 rounds/hour it can hold a bullet during manual cycle.

[croue]