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Should i crimp my 9mm loads?

Discussion in 'Reloading' started by November Sunrise, Sep 23, 2010.

  1. I have seen more than a few contradicting articles regarding the need for crimping straight wall cased ammo. Specifically the 9MM. I currently do give mine a light crimp only because i don't feel comfortable NOT doing so. My Lee dies are new and they size the case wall to a smaller diameter than the inserted bullet. The finished rounds have a bell appearance and i am sure the bullet will be held in place sufficiently by this alone but i still give em a little crimp to ensure the flare on the case mouth is gone.What are your thoughts?
  2. ron59

    ron59 Bustin Caps

    Jan 3, 2009
    Smyrna, GA
    What you said. You're not really "crimping", but instead removing the flare. You can even measure it... at the case mouth, desired diameter is something along: .375-.377 "

  3. fredj338


    Dec 22, 2004
    Always, regardless of what ever article you read, always crimp psitol ammo, always. It's more rleiable & more accurate, why not?
  4. jdavionic

    jdavionic NRA Member

    May 1, 2008
    I always crimp 9mm rounds. The last thing I was is a bullet getting pushed back in the case while I shooting a match.
  5. Boxerglocker

    Boxerglocker Jacks #1 Fan

    Mar 6, 2003
    Lynnwood, WA
    Ditto.... .377 :wavey:
  6. njl


    Sep 28, 2000
    Or...bullet diameter + (brass thickness at the mouth * 2).
  7. lanternlad

    lanternlad Mythmatician

    Mar 28, 2008
    I remember reading an article that said crimping was better because it allowed more pressure to build up behind the bullet instead of escaping around the sides. This gives the bullet more velocity and a harder hit upon impact. I'm assuming the pressure escape of crimped vs uncrimped would be negligible, but hey, with 9mm you need all the power you can get. :)
  8. Zombie Steve

    Zombie Steve Decap Pin Killa

    May 31, 2007
    Old Colorado City
    Taper crimp to remove the flare you put on before you seated the bullet. That's all. Neck tension holds it. I think performance-wise, roll crimps for bullets with cannelures (mostly revolver rounds) can help get a more consistent ignition and leave less unburnt powder, but again, a taper crimp doesn't hold the bullet in place, neck tension does.
  9. fredj338


    Dec 22, 2004
    ZOmbie, right again. You get a little bit of tension out of a good TC, but it's all about neck tension.:wavey:
  10. 1glockfan23


    Mar 11, 2010
    I use the light taper crimp that the Lee seating die provides, and is usually sufficient for my 9mm and 40 rounds. I use the Lee Factory Crimp die on my revolver ammo since I load lead bullets in those.
  11. dudel


    Dec 10, 2008
    Texas Hill Country
    Always crimp. Pistol rounds that headspace on the case mouth (like 9mm) get a taper crimp. Pistol rounds that headspace on the rim, get a roll crimp. Doesn't matter what kind of die you're using. Lee provided a crimp die in the set. What you percieve as neck tension means nothing.
  12. Colorado4Wheel


    Nov 2, 2006
    You will use a crimp die to remove the flare but you don't actually crimp it. Look in your Lyman manual and you will see even when they talk about crimp they are not bending the case in towards the bullet. So it's symantics for 9mm. Below is drawing of what Lyman recommends with crimp. Notice it has no inward turn of the case.

  13. sig2009


    May 3, 2005
    I try to keep at .377. If you go down to .375 with a plated bullet you are putting a deep groove into the bullet and you will be cutting into the plating.
  14. sig2009


    May 3, 2005
    I stopped using the Lee FCD because it was resizing the bullet.