crimp question?

crimp question?

This is a discussion on crimp question? within the Reloading forums, part of the Defensive Ammunition & Ballistics category; how do i know if i have enough crimp on my 9mm rounds?? i do need crimp right?? thanks...

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Thread: crimp question?

  1. #1
    Senior Member Array bigo5552000's Avatar
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    Question crimp question?

    how do i know if i have enough crimp on my 9mm rounds?? i do need crimp right??

    thanks
    "Any intelligent fool can make things bigger, more complex, and more violent. It takes a touch of genius -- and a lot of courage -- to move in the opposite direction."-Einstein


  2. #2
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    Since the 9mm headspaces on the case mouth you don’t crimp but just remove the belling that allows the bullet to be inserted into the case.

    Some Random Thoughts on Headspace, Headspace Measurement and Gauges
    When you have to shoot, shoot. Don't talk.
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    VIP Member Array frankmako's Avatar
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    i use a factory taper crimp die from lee. works well. i use the bullet seating die to seat the bullet and take out the belling.
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    Senior Member Array bigo5552000's Avatar
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    im using rbcs...the instructions said screw down tell it touch ramp then add a 1/4-1/2
    "Any intelligent fool can make things bigger, more complex, and more violent. It takes a touch of genius -- and a lot of courage -- to move in the opposite direction."-Einstein

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    VIP Member Array dukalmighty's Avatar
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    That should be pretty close,after crimping the bullets,you should be able to slide them in and out of the barrel chamber without hardly any resistance.
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    --Mayor Marion Barry, Washington , DC .

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    Member Array speedjunkie's Avatar
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    I'm using the factory crimp die from Lee in .45acp and will do the same for 9mm when I start loading that. Lee says to touch, then 1/2 to 1 turn more, depending on how much crimp you want. .45acp seats the same way as 9mm, so I only go 1/2 turn and it's good!




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  7. #7
    VIP Member Array Tubby45's Avatar
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    Quote Originally Posted by bigo5552000 View Post
    im using rbcs...the instructions said screw down tell it touch ramp then add a 1/4-1/2
    Crimping is basically moving the case mouth towards the central axis of the casing.

    What you are doing in pistol cartridges that headspace off the mouth (ie headspace is measured from casehead to casemouth and relies on the casemouth to be square for accurate measurement) is removing the belling or case mouth expansion you made prior/during powder charging.

    Best way to know if you are doing it right is to measure your crimp.

    A case mouth is generally .010" thick. Double that and add the actual bullet diameter. For 9mm and a .355" bullet, your crimp should measure .355+.01+.01=.375 with a +/- .002.

    Crimping in a pistol cartridge is just flattening the case mouth along the bullet shank, nothing more.

    Here's an example with .45 ACP.

    Measure crimp here.


    .01+.01+.451=.471

    This one is a bit tight, but .469" to .471" is acceptable.
    07/02 FFL/SOT since 2006

  8. #8
    VIP Member Array Tubby45's Avatar
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    If you are seating and crimping in the same step (with the same die) then:

    Set the bullet seating depth
    • Put an empty case in the shellholder and raise the ram. Turn your die down until it contacts the case mouth and turn it back up a half turn. Finger tighten the lock ring (more adjusting this later.)
    • Set your seating depth screw to the highest point. Now put a bullet on the case and raise the ram (case into die). Screw the seating screw until bullet contact. Lower the ram a bit, turn the seating screw a bit at a time until the OAL is set.


    Result is you have a bullet seated to the cartridge OAL (overall length).

    Next, we set your crimp.

    • Once OAL is set, back the seater screw out fully. Loosen the lock ring.
    • Turn the die down until the desired amount of crimp is met. Remember the optimal is .375" for 9mm.
    • When you have the desired crimp setting, raise the ram, set the lock ring and tighten. Then turn the seating plug down until it stops against the bullet.


    Now your seating die will seat the bullet to depth and crimp.

    The seater plug (screw) will only adjust depth. The crimper is in the shoulder of the die body.

    With a separate seater and crimp die, you make the OAL adjustment with your seater die and the crimping adjustment with the crimp die.
    07/02 FFL/SOT since 2006

  9. #9
    VIP Member Array Stevew's Avatar
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    All good advice. I also make sure I can't spin the bullet in the case. I make sure they chamber and shoot ok. I shoot all but one out of the mag and then check the last bullet to make sure it hasn't moved under recoil. I like to put new cases on the trimer and make sure they all the same length and squared up. Then I keep them separated by the batch.
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  10. #10
    VIP Member Array Tubby45's Avatar
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    If you can spin your bullet, your sizing die is seriously out of whack.

    The sizing die controls the bullet tension, not the crimp.

    As I said before (in several other threads), trimming pistol brass is a waste of time and money.
    07/02 FFL/SOT since 2006

  11. #11
    Senior Member Array bigo5552000's Avatar
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    thanks for the info!
    "Any intelligent fool can make things bigger, more complex, and more violent. It takes a touch of genius -- and a lot of courage -- to move in the opposite direction."-Einstein

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