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taper crimp on 40 s&W and 10mm

Discussion in 'Ammunition & Reloading' started by scrandall01215, Jun 22, 2013.

  1. scrandall01215

    scrandall01215 Washougal,WA Well-Known Member

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    I'm new to reloading and was wondering how much of a taper crimp should I use? I crimped my first loads with 2 thousanths of a inch. the case on my 10 mm measured .419 I set the crimp @ .417 is this enough?

    Thanks Stacy
     
  2. XSubSailor

    XSubSailor SW WA Active Member

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    A taper crimp should only remove the belling made by the expander. So the final outside diameter should equal the bullet diameter plus twice the case thickness.

    Ex: if you're using .401" dia bullets and .010 thick brass, the final diameter at the case mouth should be .401 + (2 X .010)= .421"

    Overcrimping does not increase neck tension...it only distorts the brass and/or bullet.
     
    bcdon and (deleted member) like this.
  3. bballer182

    bballer182 Molalla Active Member

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    What he said.;)
     
  4. deadshot2

    deadshot2 NW Quadrant WA State Well-Known Member

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    The only time the term "crimp" is appropriate is when the bullet has a cannelure and you are actually rolling the mouth of the case into it.

    For autoloaders all that you are doing is like XSubSailor said, returning the mouth of the case to where it will touch the bullet. It's really easy to decide how much one should adjust the die. Start with the seating die backed out and then check a finished cartridge by looking at it. Does the case mouth touch the bullet? If not, screw the die in a little more and check again. A properly "crimped" cartridge for an autoloader will freely drop into the chamber of a removed barrel.

    For most, adjusting a seater die to both seat and crimp can be a bit of a hassle. When I last used the seater die to crimp my 9mm rounds (same needs as the 40 and 10mm) I backed the seater adjustment back, adjusted the die body until the case mouth just came in contact with the case, then adjusted the seater plug for correct OAL. Today I just use a Lee Factory Crimp Die and put it in the last station of my progressive.

    If you want to play around with a caliper and measure, fine, but your eyeball will tell you all you need to know. Just enough to touch and not so much it distorts the bullet.
     
  5. scrandall01215

    scrandall01215 Washougal,WA Well-Known Member

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    Thanks guys I was totally under the wrong impression as to why you're supose to crimp a semi auto.
     
  6. rgold1963

    rgold1963 Washington State Active Member

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    All of my 10mm loads are "crimped" to .423 which just removes the belling from the powder die. I have never had a problem with any bullet setback and I load full power 10mm in a variety of bullet weights.

    Ron