Corbon DPX crimp in middle of casing?

Corbon DPX crimp in middle of casing?

This is a discussion on Corbon DPX crimp in middle of casing? within the Defensive Ammunition & Ballistics forums, part of the Defensive Carry Discussions category; Purchased a new box of Cor-Bon DPX 9mm 115gr +P. I noticed the casing has a crimp in the middle, unlike my Cor-Bon DPX 38 ...

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Thread: Corbon DPX crimp in middle of casing?

  1. #1
    Member Array snakyjake's Avatar
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    Question Corbon DPX crimp in middle of casing?

    Purchased a new box of Cor-Bon DPX 9mm 115gr +P. I noticed the casing has a crimp in the middle, unlike my Cor-Bon DPX 38 Spc, or other ammo.

    Does this weaken the casing?
    Will this affect reliability?
    Is this normal?
    Is this a defective box of ammo?
    Should I be concerned?
    Should I return the box of ammo?

    IMGP1290-1.JPG

    Jake


  2. #2
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    The crimp is to prevent bullet push back when it hits the feed ramp as the slide slams it into the chamber. If the bullet gets set back into the case, case volume is reduced, pressure is increased, and a catastrophic failure (kaboom) may ensue. If you routinely load the same cartridge, check its overall length with a new one to be safe. The crimp doesn't materially affect the safety of the round.
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    Senior Member Array GentlemanJim's Avatar
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    The above is correct except the proper terminology is cannellure. (not sure of the spelling)

    Jim

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    The ammo is just fine; it's made that way.
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    Senior Member Array IAm_Not_Lost's Avatar
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    I think what he is asking is why the crimp is down so low compared to other 9mm bullets. The reason it's way down in the middle on the DPX round is because the bullet is all copper, and copper is lighter than lead, thus the bullet has to be longer to reach an adequate weight, i.e. the crimp - which as others have explained prevents setback - is lower.
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    Member Array snakyjake's Avatar
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    Good information so far. But why is the crimp on 9mm different than DPX 38 spc +P?

    IMGP1292-1.JPG

    Here's what the DPX9 looks like from Cor-bon's website...no crimp in the middle:

  7. #7
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    There are several manufacturers that have crimps in the middle of the case. Dont worry about it, it is meant to be there.

    Does this weaken the casing?
    No.

    Will this affect reliability?
    No.

    Is this normal?
    Yes.

    Is this a defective box of ammo?
    No.

    Should I be concerned?
    Absolutley not.

    Should I return the box of ammo?
    No.
    Majorlk likes this.
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    There are times when bad rounds make it past Quality Control,therefore asking questions is the only way to get an answer that can put you at ease.In some cases the bullet itself has the cannelure on it,and it is usually seen right at the case mouth
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  9. #9
    RKM
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    The DPX I carry in my G30SF has a crimp. It's to prevent bullet set-back during repeated chamberering or recoil. BUT... I've noticed with my DPX, after a round has been chambered numerous times, the bullet will NOT set-back but you will be able to spin the bullet in the casing. The round will not pull out of the casing or be able to be pushed in (set-back). It merely sits loose enough to be able to spin it. This however has no affected on shootability or reliability that I've found shooting them from my 1911. I think have a cannelure on the bullet itself would fix both setback and the "spin" issue I've come across.

    I've also found that bullet set-back can be grossly exaggerated. Unless the set-back is very drastic or will not chamber due to it, it's LIKELY not to cause problems. I, unknowingly, shot pretty bad set-back rounds out of a Kel-Tec with not affects. If any firearm will explode due to set-back, I'm sure a Kel-Tec would. They're great firearms for a lot of people, but let's admit.... they're far from high quality. If you can not see the set-back with your naked eye (even if you can and it's very slight), it's not going to cause problems, according to my experience.

  10. #10
    RKM
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    Quote Originally Posted by snakyjake View Post
    Good information so far. But why is the crimp on 9mm different than DPX 38 spc +P?

    IMGP1292-1.JPG

    Here's what the DPX9 looks like from Cor-bon's website...no crimp in the middle:
    Mostly because a .38 isn't going to be rammed into a chamber, thus set-back probably won't happen in a revolver.... though it's not unheard of, due to recoil alone.

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    Member Array forestranger's Avatar
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    Just got 4 boxes of 9mm DPX delivered this week, All had the "crimp" where my older DPX did not. Was glad to see it on new ammo.

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    Quote Originally Posted by forestranger View Post
    Just got 4 boxes of 9mm DPX delivered this week, All had the "crimp" where my older DPX did not. Was glad to see it on new ammo.
    Alternately, revolver rounds are subject to "bullet jump" where the recoil causes the the bullet to extend from the case, sometimes to the extent it locks up the cylinder. Now you have both sides of the bullet movement issue.
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