30-357 maximum

fineredmist 7,

The function of the Lyman M-die is to expand the inside of the neck to a proper diameter with a slightly larger diameter short step (and flare if desired) at the mouth. That step receives the base of the bullet inside the neck rather than setting on top of a flared only mouth as with the normal 3-die set expander plug die. This step does two things: 1) It allows you to start the bullet straight by hand, and hold it there, before entering the seating die. 2) It prevents the case mouth from shaving lead from the sides of the bullet during seating, especially so with plain base bullets. In my opinion, the M-die is much better than flaring only with 3-die straight case dies and a necessity with 2-die bottle neck dies as they don't flare the mouth at all. Thus, with 2-die sets, you are trying to cram a larger diameter soft lead bullet into a smaller diameter harder brass case mouth hole with the result being...shaving of the bullet. This does not help accuracy, regardless of how perfectly you may have cast, sized, lubed, and handled the bullets prior to seating. Most Lyman 3-die sets now come with the M-die as their expander, but they can be bought separately to add to typical 2-die sets for bottle neck cases. I've used them for all my cast bullet loading for over thirty years. If you go to the Lyman web site, I think you can see a graphic and description of the die, at least past catalogs have shown it. 

Here is a 30 cal. example from the Lyman web site.

Rifle (M) Die 30 L (.308 Win. (.307 Win.))

Improves accuracy of cast and jacketed bullet reloads. Doesn't stretch cases as does standard expander button. Extends case life. Many reloaders consider Lyman's Neck Expanding (M) Die a valuable tool for improving the accuracy of their reloads. The die's expander plug has two steps.

http://www.lymanproducts.com/lyman/dies/precision-rifle-dies.php>« Return to Die Selector>

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