[clement1]

In using a set of dies other than actual 9mm Largo for reloading 9mm Largo rounds, which would be preferrable - 9mm Luger dies OR 38 ACP/38 Super dies?​

 

[Oyeboten]

Possibly....38 Super Die to re-size...and, 9mm Luger Die to re-size as far as it can, and then use it to crimp...and or it may depend somewhat on the actual Chamber of the individual Pistol, and exactly what Bullets and or diameter Bullets one will be using, as for whether it minds the Cartridge being re-sized to be a teeeeeny bit fatter, or not, as the 9mm Largo Cartridge Case is just a little less in diameter toward the mouth, or is thinner walled I think, than the .38 Super.


Far as I have heard, people use .38 Super dies for the whole process and it works out fine for them, but, one would have to see for one's self, and or see what one's particular Pistol will get along with to know what is best for one's own uses on that.

 

[partsproduction]

Considering that changing a 9MM Largo to shoot 38 ACP or (With stupidity) 38 Super amounts only to opening that rim area at the back of the chamber (And/or breechface if spotfaced for the rim) it's easy to see that 38 Super dies do nicely, and I've loaded quite a few with 38 Super dies. The rim of the 9MM Largo is 14 thousandths smaller which is the main difference dimensionally, but I am pretty sure I use the 38 S shell holder too. But look at the reloading books at the cartridge dimensions for both to make your own mind up.
9mm Largo, rim dia. .392, case dia forward of groove .390, case dia at mouth .379, case lth .910
38 Super, " " .406, " " " " " ..384, " " " " .384, " " .900

 

[clement1]

If you click on this composite image it shows the dimensions of the three cartridges in question. It seems that the INNER dimensions as well as the taper case closest to 9mm largo seems to be 9mm para...however the length is definitely closest to 38 Super. Would not the 9mm dies set either screwed down or out (can't figure out which way to go) would be best. But this goes against the common wisdom of substituting 38 Super dies...even Lee says on their website that 9mm Largo = 38 Super for substituting dies.

 

[MGMike]

The problem with trying to calculate all this based on dimensions taken from a book or manual is that the published figures bear little relation to reality. At best they are purely nominal, not actual. If you doubt this, gather up a wide variety of cases from various lots of 9mm Largo, .38 ACP, .38 Super and 9mm Steyr and measure them with a micrometer. You'll find more variation between different lots of 9mm Largo from different factories than the difference between 9mm Largo and 9mm Steyr. And, except for the larger semi-rim, the same is true when Largo is compared to the .38s. Then make Cerrosafe castings of some sample chambers, and discover what an irreconcilable puzzle you wind up with.

In the end, the minor dimensional differences don't really matter. The important thing is that, after re-sizing, the cartridges will feed smoothly and without binding in the particular chamber you plan to shoot them in, and that the rim is small enough to fit in the slide face counterbore, and that everything is sufficiently concentric that when the cartridge is chambered, the breech will close comfortably in a blowback like the Astra 400, or lock up correctly in a Star. Then select the lightest load that will reliably function the gun. These guns are old-timers; give them something soft that their old teeth can chew.

M