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Bullet crimping - 10mm G20

Discussion in 'Reloading' started by rvrrat14, Nov 15, 2011.

  1. rvrrat14


    Sep 21, 2010
    Central Texas
    New to reloading the Glock. What's best method for crimping 155 gr bullets? Lee FCD or standard RCBS taper crimp die? Do any bullets have cannelures?
  2. F106 Fan

    F106 Fan

    Oct 19, 2011
    The 10mm is a straight-wall case. As such, the cartridge headspaces on the front of the case to a ridge in the chamber. If you were to roll crimp the case, headspacing would go right out the window.

    So, a taper crimp die is used to straighten out the case mouth which was expanded to facilitate seating the bullet.

    There doesn't seem to be a lot of love on this forum for the FCD. It is a solution to a problem that just doesn't exist.

    When setting the taper crimp die, read the instructions because you don't want to over-crimp the case. Just straighten the wall and perhaps just a little bit more to keep the bullet from moving back in the case during recoil.

    I haven't really had an issue but I understand that the taper needs to be just about zero for plated bullets.




    Dec 20, 2002
    I use a taper crimp die to remove the flare from bullet seating and maybe add just .002" (barely visible) crimp.
    Auto pistol bullets don't have cannelures because they don't need much crimp.

    Make sure you use an absolute minimum amount of flare to seat the bullet. Too much expansion and flare will reduce the case mouth tension (bullet tension) and will increase the chances of the bullet setting back into the case during the feeding cycle.
  4. Colorado4Wheel


    Nov 2, 2006
    You actually are not "crimping". All you are doing is removing the flare. You can do that with the most basic of crimp dies.
  5. fredj338


    Dec 22, 2004
    Well, you are crimping by definition, the seating die seats & crimps; roll crimp for revolvers, taper crimp for semiauto. What Steve said is correct, the amount of crimp is minimal for a semiauto round. Pull a bullet after seating & crimping. If you can see an identation all around, that is too much crimp. F106 is correct, the LFCD is a solution to a non existant proplem. Before the LFCD, we all somehow managed to reload 100s of 1000s of reliable/accurate rounds w/o that little tool.
    Last edited: Nov 16, 2011
  6. Kwesi


    Sep 23, 2006
    Does the visible ring on the case at the base of the bullet have anything to do with crimp or is this due to resizing the case several times? I noticed my factory ammo does not exhibit the same ring.
  7. F106 Fan

    F106 Fan

    Oct 19, 2011
    That bulge is a result of the case mouth expanding to hold the bullet. It doesn't mean anything.

  8. Kwesi


    Sep 23, 2006
    Ok but why does the factory ammo not have that? Virgin brass?
  9. F106 Fan

    F106 Fan

    Oct 19, 2011
    I don't really know. Perhaps they don't size the brass down as far as most reloading dies. Clearly the outer diameter at the bullet will be the same for factory or reload so the difference is in the case diameter below the bullet.

    Or maybe they use some kind of die and resize the entire cartridge when they seat the bullet.

  10. Kwesi


    Sep 23, 2006
  11. BK63


    Sep 15, 2005
    I taper crimp anything straight wall auto and it always feeds just fine.
  12. Bret

    Bret Crimping Master

    Jan 21, 2003
    North Georgia
    It has nothing at all to do with the crimp and has nothing to do with how many times the case has been sized. Basically, your sizing die sized down the case a little more than is necessary for the particular case and bullet combination that you're using. If the case was sized down ever so slightly less, then you likely wouldn't see the ring at the base of the bullet. Understand that the manufacturer of your sizing die has to make the carbide sizing ring small enough that it will adequately size down the smallest diameter bullet and thinnest case combination. If you're bullet is the normal diameter or more and/or your cases are normal diameter or more, you'll likely see this ring. This ring is typically called the coke bottle effect. It absolutely will not cause a problem at all. It does tell you that you have plenty of tension between the case and bullet. Don't worry. You won't ever have too much tension. Take a look at some more factory ammo. If you look at it in the light at the correct angle, you can often see the same ring.
  13. Taterhead

    Taterhead Counting Beans

    Dec 13, 2008
    Boise, Idaho
    My RCBS seating/crimp die has loaded thousands of 10mm rounds. With Starline brass, the diameter of the brass after crimping is between 0.420-0.423" depending upon theload. At diameters less than 0.420" i start to see deformations on the bullets.

    Plated bullets just get the bell ironed out. Seating a crimping in separate steps has given best results for plated. Heavier charges with jacketed bullets are crimped to around 0.421". Differing case lengths will obviously affect the crimp diameter. +/- one thousandth on the extreme. Good enough for me. Some guys sort pistol brass by length. I don't bother.
  14. freakshow10mm

    freakshow10mm 10mm Advocate

    No, it usually means the bullet is seated too deep. This means the bullet base is expanding the internal taper of the case and creates a bulge. The correct way to remedy this is to seat to a longer OAL. If you're at 1.260" SAAMI and still getting this, go to a shorter (ie lighter) bullet.

    See above. Correct sizing and correct bullet seating depth for that bullet.