Causes of Keyholing

Discussion in 'The Ammo & Reloading Forum' started by The_Vigilante, Jun 5, 2009.

  1. The_Vigilante

    The_Vigilante New Member

    Apr 28, 2008
    El Paso, Texas
    I am currently reloading 147g LFP 9mm and have been using VV N320-3.6g. Using COL of 1.135. A lot of my reloads are keyholing. What is the best way to troubleshoot this problem and determine the cause? Thanks
  2. johnlives4christ

    johnlives4christ Former Guest

    Apr 28, 2008
    im not a reloader, but best i recall keyholing is caused by too heavy a bullet weight, heard the rifling will not stablize it and it flops like a chicken bone in a dogs gullet when it's flyin through the air. dont know if all this is true though


  3. Claude Clay

    Claude Clay New Member

    May 26, 2009
    Central CT
    what is your target. if the paper is loose to the backing the bullet often tears the paper as it pulls it to the backing giving the appearance that it is the bullet that is tumbling.
    on the other hand too heavy pushed too fast in a fast twist can lead to instability's--try lighter loads and/or 124 gr.
    what model gun? what type of bullet-- hard lead, soft lead? diameter? most 9mm is .355 jacketed and .356 lead (or plated). some lead is .357 but pressure may become an issue. i dont find your powder listed but 340 is for lighter bullets and it is slower burning than 320. i have had good with bullseye for bbls 4" & under. otherwise power pistol or tightgroup.
    Last edited: Jun 5, 2009
  4. Suwannee Tim

    Suwannee Tim New Member

    Feb 11, 2009
    It is most likely that the twist of your rifling is just too slow to stabilize this boolit. Cast boolits are longer than swagged for the same weight and a longer boolit requires a faster twist. Did you cast these boolits or buy them? Why not switch to a lighter and more easily stabilized boolit?
  5. Suwannee Tim

    Suwannee Tim New Member

    Feb 11, 2009
    Dat's funny.
  6. The_Vigilante

    The_Vigilante New Member

    Apr 28, 2008
    El Paso, Texas
    Thanks for your replies and suggestions. These are 147g bullets I purchased from Missouri Bullets. Supposed to be hard-Brinell=18 with .356 diameter. Pistol is a CZ-SP01 Phantom. Target is a cardboard IDPA target so that's not it.
  7. Suwannee Tim

    Suwannee Tim New Member

    Feb 11, 2009
    Other possible causes of keyholing, very unlikely in your case: The bullet is too small for the barrel and doesn't get spun up. Or, the bullet is so soft and the velocity so high that the rifling strips the bullet, I mean boolit and the boolit doesn't get spun up. Another possibly is the bullet, I mean boolit is of an inherently unstable shape, like a hollow base wadcutter turned backwards.
  8. ampaterry

    ampaterry *TFF Admin Staff Chaplain* Staff Member Supporting Member

    Dec 20, 2008
    West Tennessee
    At the risk of stating the obvious -
    Have you checked the condition of the rifling?
  9. carver

    carver Moderator Supporting Member

    Don't know anything about re-loading the 9mm, but how fast is this load supposed to moving? Too fast will lead the barrel, and then you won't get any spin on bullets fried after that.
  10. Suwannee Tim

    Suwannee Tim New Member

    Feb 11, 2009
    I bought a Smith and Wesson model 52, 38 special semi-auto off GB, took it to the range. The first few shots were all over the paper then I began seeing keyholes and even missing the paper. The gun was tight and in great condition. Evidently some previous owner had been OCD about cleaning and had cleaned the rifling right out of the barrel. What little rifling was left was almost invisible.
  11. DWARREN123

    DWARREN123 New Member

    Aug 23, 2003
    I would look at your powder for this problem this time. Sounds like it is not the right one. 147gr in 9mm should stabilize if the rifling is good and the bullet is lubed properly with the correct powder.
  12. S&W-4me

    S&W-4me New Member

    Mar 24, 2009
    Connecticut, USA
    Another factor often overlooked is the squareness of the barrel crown or chamfer in relation to the bore. If the crown is not square to the bore it allows gas to escape on one side of the bullet before the other. This causes the bullet to be unstable. This sometime only effects the longer heaver bullets because they my be borderline with the twist in your barrel. Offhand I would say the barrel twist, and charge, is not right for the bullet you are using. This is the most common cause for keyholing. regards
    Last edited: Jun 6, 2009
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