M die question

[cp478]

My uncle just purchased a set of lyman dies for 45 acp that have the M expander. He is having major troubles on the expander step. He says that it is leaving a large bulge in the center of the cases. From what I have read people really seem to like these expander dies , there has to be a trick to them.

[cdet69]

It sounds like it is set to low. The expander should just touch the case mouth with a little more depth to get the correct belling. Just one of those trial and error until the depth is set correctly.

[462]

Did the dies come with instructions? If not, call or e-mail Lyman, for a set. Also, their web-site has a diagram and an explanation of how the die works.

In the meantime:
1. With an empty case in the shellholder, raise the ram, run the die body down till it contacts the case, and tighten the die's lock ring.
2. Screw the expander stem down till you get the right amount of mouth expansion (just enough that a boolit enters the case mouth abouth 1/16") then tighten the stem's lock nut. This step will take time and experimenting.

If you look at the expander plug, you will notice that it has three diameters. The first, and smallest, expands the case to under the cartridges nominal diameter. The second step is what expands the case mouth to a bit more than nominal diameter, and installs a 1/16" step. The largest diameter will put a huge flair on the case mouth. I've never found a need for the flair.

[trk]

My uncle just purchased a set of lyman dies for 45 acp that have the M expander. He is having major troubles on the expander step. He says that it is leaving a large bulge in the center of the cases. From what I have read people really seem to like these expander dies , there has to be a trick to them.

What you see is the case sized right-much small by the sizing die and then the case opened up to the necessary size by the expander.

I've found one doesn't have to size quite so much, cases still chamber with good clearance.