Lyman "M" Die

[35isit]

I'm going to be loading 25-20WCF using a Lyman "M" die to expand the case mouth. Do you have to take the expansion out after seating the bullet? Sorry I spelled it correctly. Going to be running j-words in a Contender. I know they are used for cast all the time.

[richhodg66]

I don't use them for jacketed bullets, only cast. I've never done anything to rounds after loading them unless I crimp for lever guns.

[HangFireW8]

Do you have to take the expansion out after seating the bullet?

The answer is "depends".

It depends on whether using the M die leaves a funnel shaped flare or not, or enough of a mouth step to interfere with feeding or chambering. And that depends on the thickness and hardness of your brass, size of your expansion ball, that size in relation to the M die, and whether you use the step on the M die or just the initial shank.

Load up a few dummies and examine them carefully, and if they look good see if they feed and chamber OK.

[Mk42gunner]

As Hangfire said-- depends.

.25-20 brass is notoriously thin (even the necked down .32-20 brass that I have is delicate) and I have only loaded cast in mine, no jacketed. You may not even need to expand the neck / mouth to seat jacketed projectiles, I know I never expanded the necks of .30-30 when I was loading jacketed only when I was using cast.

It really depends how much you expand the case mouth, if there is a noticeable flare, then you should probably remove it maybe not actually crimp by running the seating die a bit deeper.

Robert

[rbuck351]

I don't bell the mouth on 25/20. I just open the neck with the bottom part of the m die but I do champer the inside of the neck more than usual with the lyman long taper tool.

[35isit]

Thanks guys. As you all know 25-20 brass can be unobtainium sometimes. The fellow I got the barrel from used the "M" die to aid in seating bullets. I probably will also, don't want to lose any brass.

[greenjoytj]

If you don’t want to loose brass, be sure to do the absolute minimum case mouth expansion as the expansion and contraction weakens the case mouth till it splits.
You may need to think about annealing the case necks of your brass more often.

[44magLeo]

Would this cartridge be a good candidate for a neck sizing die that uses the inserts? That way you could use the insert that gives the necessary sizing but with out needing to be expanded.
Leo

[HangFireW8]

Would this cartridge be a good candidate for a neck sizing die that uses the inserts? That way you could use the insert that gives the necessary sizing but with out needing to be expanded.
Leo

I'm biased towards bushing / insert dies, but another alternative is a custom made die. I think Lee and Forster will still make dies to order, at least they did until recently. In order to get the right dimensions, you have to load a few dummies, and maybe send one in.

[FergusonTO35]

I ordered me some M dies for .30 WCF and 9mm Luger, as I think I am having some trouble with boolits being sized down when they are seated in these cartridges. I size my .30's to .310, the 9's to .357. Any advice or suggestions on how best to use them for these cartridges?

[Livin_cincy]

I ordered me some M dies for .30 WCF and 9mm Luger, as I think I am having some trouble with boolits being sized down when they are seated in these cartridges. I size my .30's to .310, the 9's to .357. Any advice or suggestions on how best to use them for these cartridges?

If your goal is to over/ max size lead bullets you will want to verify they will chamber before you make to many of them.

The Negative is that you cannot use a powder thru die that operates a powder measure automatically. So you add a step to your process. Lyman does make a pistol caliber powder thru 'M' die that lets you use a manual powder measure on top.

[FergusonTO35]

Thanks, I don't mind an extra step in the loading process.

[MostlyLeverGuns]

The only rifle cartridges I crimp after using a Lyman 'm' die are tube feed lever actions. I do not 'bell' or flare with an 'M'die, the second step, about .0025"-.004" larger than the expander (e.g .3065-.3095 for 30 cal) is used to make a small step for the bullet to start, about the depth of a gas check. I have polished/chamfered a couple sharp chamber edges so a case mouth would not catch on the edge of a chamber when feeding. In your single shot feeding should not be an issue. I do not crimp or even bother with reducing the case mouth expansion for 243, 308, 300 Savage, 303 Savage, as long as feeding is smooth. I do use the 'M' die for both jacketed and cast bullets, though diameters are different.

[FergusonTO35]

Good idea, thanks.

[FergusonTO35]

Tried out the M die for 9mm last night. It works great! This die seems to expand in a more gradual manner than the Lee die does. Also, it is just what I need for hard European brass. That stuff shakes my reloading bench when it comes out of the Lee expander. Really like this die, will get 'em for other cartridges.

[MOA]

I use them for both jacketed and cast. Cast gets the most use but it's nice to have them if you need them for j words too. You can also I think go to NOE for specific expanders if Lyman does not either make what you need or their sizes are just not running true to their stated dimensions. Layman's 9.3 was just not big enough for my cast .369 boolits. Most likely would work for someone using it for a 9.3 j word though, but not my cast ones.

[cwlongshot]

I agree 100%. I have seen accuracy improvements when using aMdie in jacketed.

Yes utsa extra step. But many if my cf rufle
Loads are single stage anyhow so no big deal really and since I do this for enjoyment as well as increased accuracy its a no brainer.

Good luck, hopefully as this is a few months old post, you have already seen the improvemnts these dies afford

CW