Die setting for 10mm

[RickCoop]

Hello. I have the Lee .40 S&W /10mm four die set. I have been loading .40 S&W for a few weeks now. I am going to load a few 10mm but was wondering about die length setting. The instructions with the set say to back off an extra 1-3/4 turns for the expander and bullet seating dies for magnum cases. Is this what should be done to set up for the 10mm? Thanks for you help.
Rick

 

[steve4102]

Back the expander out until it gives you the desired flare, however many turns that is.

 

[Reloadron]

Sounds about right. A nominal .40 S&W case length is right about 0.850" and a 10mm Auto case length is right about 0.992" do the difference is 0.992 - 0.850 = 0.142. The typical die thread pitch diameter is 7/8 x 14 so you will get 14 turns = 1 inch of travel of the die down or up. A single turn of the die = 1 / 14 = 0.0714 inch per turn. Rotating the die 1.75 turns out as suggested will move the seater plug up 1.75 x .00714" = 0.125" approaching the approximate difference between the two cartridge lengths. The SAAMI cartridge lengths both have an allowable 0.010 minus on their max limits which I posted.

Just adjust the die up a few turns and then slowly run the die in until you get a nice bell opening at the case mouth to seat your bullets, the above is just to give you an idea of how the 1.75 turns was derived..

Ron

 

[Unclenick]

Should actually be just about 2 full turns out on the expander die:

(0.922 inch - 0.850 inch) × 14 turns/inch = 1.988 turns

But the maximum lengths of the two cartridges are a smaller difference, so the bullet seater should be about 1.5 turns out to get the cannelure to the case mouth.

(1.240 inch - 1.135 inch) × 14 turns/inch = 1.47 turns.

I think the 1.75 turns number is just to put you between those two numbers and make the instructions simpler. Also, you may find some bullets have a nose profile that sticks out too far in the 10 mm when you do this. Check with your caliper.