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tercel89

Crimping pistol ammo cases

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I am confused on the crimping of pistol ammunition cases. I am going to start reloading 9mm and I have all the equipment to start but I am still a little confused on the crimping part. I have Lee dies and they include the bullet seating and crimping die . 

 What I dont understand is the crimp. I thought that crimping a bullet causes a little wrinkled ring around the case where the crimper would squeeze it to hold the bullet in place. But according to these bullets I have I must be wrong .I have my duty 9mm and the gold one is a target 9mm . Both have smooth cases. I dont see where the case is squeezed inward to hold the bullet inside . It looks like the bullet is just pushed in . 

 So someone please explain to me the crimping process in plain english . Sorry but I am still learning . Thanks in advance . 

[URL=http://s768.photobucket.com/user/tercel89/media/bullets_zps768263d2.jpg.html]bullets_zps768263d2.jpg[/URL]

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With 9mm it's really not so much crimping. You have to slightly bell the mouth of the case to set the bullet in. Then your seating die needs to be set so thet it seats the bullet and remove that slight bell. The 9mm round is a slightly tapered round and not a straight wall round like a .38.

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In 9mm the cartridge seats on the case mouth so they will have a taper crimp. If you use a roll crimp on them they won't seat properly.
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I'm not aware of any reloading dies that produce the fluted heavy crimp seen on some magnum and +p loads, and at or near the base of the bullet.

 

Two types of crimp for the reloader, both applied to the case mouth. Pistol rounds use a taper crimp to close the case mouth after the bullet is seated. As Raoul said, this removes the belling formed by the expander die, adding only a slight inward taper to the case.  If you can see it, you probably crimped too much. Revolver rounds use either a taper crimp, or a heavier roll crimp which rolls the case mouth into the cannelure on the bullet.

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I'm not aware of any reloading dies that produce the fluted heavy crimp seen on some magnum and +p loads, and at or near the base of the bullet.

 

Two types of crimp for the reloader, both applied to the case mouth. Pistol rounds use a taper crimp to close the case mouth after the bullet is seated. As Raoul said, this removes the belling formed by the expander die, adding only a slight inward taper to the case.  If you can see it, you probably crimped too much. Revolver rounds use either a taper crimp, or a heavier roll crimp which rolls the case mouth into the cannelure on the bullet.

 

 So if I can see the tapering of the crimp then I have crimped too much ? This has helped me a bunch , thanks .

 Any other help is appreciated .

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Have you measured the diameter of your brass at the case mouth and lower for comparison? I usually see a few thou diff when the crimp is starting to engage


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I use a Lee factory crimp die on the last station on my Dillon 550 presses. I on auto pistol rounds I measure the out side diameter of a factory round, and adjust the crimp to match that. I have had great success doing this, all my ammo works just fine. 

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I just barely see a slight shine on the rim of the case from the crimp. Some 9mm bullets can set-back too easy if the case bell is only straightened out, and no crimp at all is applied. You can take a loaded round, push the bullet-end against a hard surface, push pretty hard by hand, and see if you can easily shove the bullet into the case, shortening the OAL. If it is too easy to push in the bullet with hand pressure, then it might be too easy for the bullet to dangerously set-back when entering the chamber. Which prompts me to increase the crimp a little bit until the bullet is not so loose.

Edited by Lester Weevils

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According to the SAMI specs for 9mm Luger the crimp should be applied down to 0.380". Take that with a grain of salt, though. The thickness of the brass varies from one mfg to another, the diameter of the bullets will have some variance (even within a single batch), and your brass will slightly lengthen and thin the more times it's reloaded. So, what I'm saying is there is a "standard" measurement, but it's not religion.

 

Like others said, just straightening the bell from the expanding/charging station is a great start. Shoot some rounds to see if you notice any setback (this is dangerous, can cause pressure spikes). If not, let the accuracy of the loads determine how much crimp you add, if any.

 

Remember, the less you work that brass (expanding and crimping), the longer that brass will last.

Edited by BigK
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According to the SAMI specs for 9mm Luger the crimp should be applied down to 0.380". Take that with a grain of salt, though. The thickness of the brass varies from one mfg to another, the diameter of the bullets will have some variance (even within a single batch), and your brass will slightly lengthen and thin the more times it's reloaded. So, what I'm saying is there is a "standard" measurement, but it's not religion.

 

Like others said, just straightening the bell from the expanding/charging station is a great start. Shoot some rounds to see if you notice any setback (this is dangerous, can cause pressure spikes). If not, let the accuracy of the loads determine how much crimp you add, if any.

 

Remember, the less you work that brass (expanding and crimping), the longer that brass will last.

Thanks BigK , that is good information ! 

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