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I am loading some 7.62x39 light loads for indoor use.

Question do you crimp your rounds after seating the boolit. I am thinking a light crimp using one of them Lee jobbies.
The 7.62x39 is actually .311 what is the correct M die to use for the .311 or what other type of expander does any one recommend.

I use the Lee collet crimp die and not too fierce with the pressure.
Case trim to length is essential.

Crimp is an abomination and an affront to all things holy.

The only time crimp might be necessary is in strong recoiling underlevers, revolvers or automatics when there is a chance of bullets moving in the cases in the magazines. Or when ammunition would be exposed to rough handling as in a military context for example

A primary requirement of consistent ammunition is good bullet retention, if you have that then the crimp is redundant.

Crimp adds nothing to a cast boolit load, over works your brass and impedes the consistent functioning of you lube and usually deforms your boolit. Why would anyone want to do that to their ammunition?

A 31 M die for 311, the M die idea has yet to be improved upon and is copied in spirit by makers other than Lyman.

I usually have my M die spuds made to my specifications for each boolit diameter and case neck diameter to ensure that consistent boolit retention so necessary for accurate rounds.

I usually have my M die spuds turned to fit the Lee universal expander die body and use that as it means the spuds don't need to be threaded as they do for fitting to the Lyman bodies and shanks.

If you are having to crimp then all you are doing is hiding and ignoring a bullet retention issue and it will do nothing to improve that other than tenuously hold the boolit in place.

What's an "M" die, ooman ?

Mine is a 30M short its supposed to be for the 7.62x39 but it is obviously under sized for the .311 boolit hence my question If I use the M die as designed I am shaving lead off. To get the boolit to start with out shaving lead I have a excessive flair on the case. So were do I get a 31M die. Failing that who makes your spuds for you.

Spuds ?

I just had a rummage in my stuff I have a 31M die I will have another stab at it.

There is a previous post some were describing the Lyman M dies.

Lyman M die body:
M die spud:
"A" is typically 2 thou over boolit diameter.
"B" is typically 2 thou under boolit diameter
"C" is typically just over boolit seating depth

This is the drawing I use when ordering new spuds.

M die in action:
Drawing is obviously exaggerated for illustrative purposes.

Dave I would imagine M die spuds would be well within your workplace resources, there are no doubt people and equipment within your purview that would turn you out suitable spuds.

I'd love there to be someone in the UK who would do these spuds at a reasonable cost but as yet my search has been futile.

I will have a word on Monday when I go to work I would not mind one in .314. They would not be expensive to make. Depends what the thread is.
I need to buy a lathe hmmm one that will screw cut.

Anyway back to the thread I neck sized the cases to get rid of the flair then cut them all to the same length on my Wilson trimmer.
(Lovely piece of kit) I then flared the case mouths using a M1 die and bingo sorted I seated the primers.
I then dropped 4 grains of Vit 310 into each case. I then had a thought I wonder if I can use my LeWilson micrometre seating die with my Arbor press to seat the boolits with. The answer is yes I can I am well impressed.
I cleaned every thing afterwards with Edds red. A good afternoons work job done ready to rock and roll just need to get them to the range.