Lee case mouth and Lyman M-Die

[Newtire]

I have been using my newly acquired Lee case mouth expander successfully for my pistol cases but have noticed a few times a problem. I get a noticeable bulging which is off center and the loads I loaded for my Marlin wouldn't chamber. Using the M-Die, the cases looked less like a snake that had swallowed a frog.

This is not a Lee bash but just wondering if anyone else has this same experience?

[1hole]

I like the Lyman M Dies too. They are marketed for cast bullets and are excellant for that use but they work quite well for jacketed stuff too. It's much easier to seat bullets concentric after using it.

[Bret4207]

Had a similar problem with an RCBS Universal Decapping Die. Make sure your shell holder is centered, that there is no crud in the ram blocking it in any way and that the shell holder itself is clean where the case sits. Beyond that misalignment between the die and case are the likely culprits. It's also possible the expander in the die is bent or otherwise off center.

[Junior1942]

You're probably sizing the necks too small. The M die will expand the entire neck; the lee die just bells the mouth.

[Cherokee]

Lyman M die, Lyman M die, did I mentiond the Lyman M die ?

[montana_charlie]

Yes, I have noticed the off-center expanding when using a 'custom' expander in the Lee die.
I think the problem arises because the expander plug is not anchored in position...but floats up and down in the die. This probably allows it to get off-center a little.

You can't screw the powder-through funnel adapter down enough to lock the expander plug in the die. But the bullet seater adjuster (which has the same thread) is long enough.
The question becomes...
Can you lock the expander down tight, and back the die out of the press enough to keep from driving the expander too deep in the case?

Another way to kill this bird is to buy a 'custom' expander for the Lyman die.
Buffalo Arms has them.

CM

[dromia]

I like the M dies and have one for most calibres. However sometimes I have to use both it and the Lee.

If the boolit diameter is close to the M die step diameter it can be a bit hard to start into the case.

The flare on the M die is real steep so the slightest difference in case length can give an unacceptable case mouth bell that can effect chambering.

So I use the Lee die instead after the M die for just gently giving the case mouth some flare to help get the boolit started.

Any excuse to buy more kit. :-D

[Newtire]

That sounds like a great way to do it Dromia especially if you have one longer case and the bell gets too huge. I will have to accumulate more of those things then. 8mm & .314" next. Maybe just make one & do like some guy here did to hollow point; he clamped a Lee Case trimmer base into a drill press vise and drilled them that way. Will maybe try that with a homebuilt M-die & the drill press.

[Buckshot]

You're probably sizing the necks too small. The M die will expand the entire neck; the lee die just bells the mouth.

...........This hits the main reason it happens. This and slop in the shell holder and the case in the shellholder. Most dies size the caseneck down WAY too much. And this for jacketed slugs too, let alone cast boolits we're wanting maybe 3 to 4 thousandths over common jacketed OD's.

A prime example, and I wish I had pictures of it, is the 38-55. Size dies make'em to HOLD a .375" jacketed bullet yet we want a .380 ~ .382" slug in there. The Lee dealie is going to flare the mouth only, to start it and the boolit is going to expand the brass part of the way while the brass does some sizing down of the boolit.

But, if you use a Lyman type 'M' die, it too can cause havoc with the brass. It has a parallel section below the actual flaring portion, which is better but not best. The 'M' sizer starts in but unless it, AND the casemouth are both perfectly in co-axial alignment, the 'M' spud will lean the case over to the extent the shellholder and case slop in that holder allow. Or at least to the maximum the slop allows. You end up with a case that has all the expanding done on one side!

Try this. Next time you go to size a rifle case lightly press your finger against it as it reaches the die mouth and see what happens. Or do the same thing when running it up into a Lyman 'M' die. Chances are the casemouth is gonna bang up against something. Rimless cases are BAD for it as there isn't as much there to hold onto.

Another bad one is the die set for the Russian 7.62x54R. Heck, Lee thinks you're going to be using .308" bullets when it sizes the caseneck (so it sizes to about .304"). Then you drag it back over an expander that's set up for .310" ~ .311" bullets. That means the neck ID is going to be about .309". In this and other shorter necked cases it's that while you may not be seeing a bulge (as the 'M' die has entered the shoulder area), the caseneck may/can be tilted off axis from the case itself.

..................Buckshot