9mm OAL seating problem

Discussion in 'The Ammo & Reloading Forum' started by springerbuster, Nov 15, 2009.

  1. springerbuster

    springerbuster Member

    Sep 11, 2009
    Southwest Washington
    I have been loading 9mm in hollow point and round nose. I can't seem to get a consistent over all length. I have my seating die set for 1.160 (or so I thought). When measuring the lengths of my finished rounds I have lengths of 1.155 all the way up to 1.167. I am loading on a progressive press and the problem is there before I run them through a crimp die. How much deviation should I expect on a progressive press? I might add that I am using mixed brass, but even when I compare rounds from the same brass they are different lengths. Any suggestions would be appreciated.
  2. gdmoody

    gdmoody Moderator Supporting Member

    Sep 7, 2007
    Athens, Georgia
    Mine do the same thing so I can't tell you exactly what your problem may be but the 9mm head spaces on the mouth of the case so it needs very little or no crimp. If you don't go over the maximum length of 1.169 you should be OK. I set my caliper at 1.169 and each one that I load will be put through that caliper, if they go through they are good to go! I have the same problem with .45ACPs and I do the same thing with them.

  3. 312shooter

    312shooter Well-Known Member

    Mar 17, 2008
    Las Vegas NV
    Several things come to mind, maybe try to increase the bell on the case mouth a hair, also the profile of both your seater plug and the bullet, I had the same problem using berrys bullets when I switched to Montana Gold they came out perfectly consistent.
  4. LDBennett

    LDBennett Well-Known Member

    Dec 20, 2003
    Hesperia, CA
    There's an anvil inside the seating die. It is probably not ideally shaped for your choice of bullets and certainly will vary depending on the specific bullet you are using. A machinist or even the die manufacturer can make you a better anvil, shaped to your bullet of choice. The anviles are typical just flat across but a hemispherical dome shape may minimize the damage to the bullet nose.

    If you have insufficient belling of the case mouth then you may be reshaping the nose of the bullet when you seat the bullet against the extra drag caused by the tight fit of the bullet going into the case. Hollow points are particularly bad about deforming as they are seated, as are soft lead bullets. Perhaps a better bullet is in order?.

    But 9 mm requires a taper crimp and does not have to crimp into a groove or canalure. If the OAL of the finished cartridges does not exceed the maximum OAL spec you are OK. I know it seems funny to try to get everything just perfect when reloading only to have the bullet deform and make the OAL vary all over the place but they are OK to shoot. If you are concerned about ultimate accuracy you should change to a better harder bullet and make sure you belling operation is setup correctly to minimize the force required to seat the bullets. Perhaps a better shaped anvil will minimize any damage to the nose of the bullet. A call to the die maker may get you a better anvil shape or some good advice.

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