Neck Tension (lee collet)

Discussion in 'Reloading' started by teampete, Sep 1, 2011.

  1. teampete

    teampete Well-Known Member

    Jan 17, 2011
    Hey all, you guys have helped me get into reloading and I appreciate all the help. I have a question about neck tension. I have a lee collet die and I started to use it after firing my rounds. I am a little worried about the neck tension. I can weasel a bullet into the case by hand but I am unable to pull it out by hand. To pull it out i have to grab a pair of pliers and grip the bullet. Is this enough tension? It seems that my brass that was sized with a RCBS fl die are just a tad tighter. Please let me know if I have enough tension and how I can measure the tension or anyway to tighten the tension if needed.

  2. Hondo64d

    Hondo64d Well-Known Member

    May 27, 2003
    Could be in how you have the die adjusted. Here's how I do it:

    1. Run the ram all the way to the top so that the handle is at the bottom of the stroke.
    2. Screw the collet down to the shell holder.
    3. Size a case.
    4. Try seating a bullet in the fired case by hand. If it goes in easily, turn the die down a small amount, maybe 1/8 turn and repeat the process until you have satisfactory neck tension.
    5. Set your lock ring. I replace all the lee lock rings with Forster rings. For me, unless I index mark the die and the press, The Lee lock ring allows a little too much movement when I screw the die into my press, making how far I screw the die down not repeatable from one time to the next.

    Bullet should not be able to be seated by hand and I don't like it if I can move the bullet by holding the case in my hand and pushing against my bench top.

    Another way is to measure with a caliper the neck diameter of a loaded round and keep running the die down until the neck diameter on a sized case is .002" smaller than the neck diameter on the loaded round. That should provide enough neck tension.

    If you are having to apply too much force or collapsing cases in your efforts, first make sure the collet fingers are not collapsed. If they are, spread them with a round punch or something similar. Don't get over enthusiastic with this. If that doesn't fix the problem, you may need to polish down the mandrell a little bit using a drill and emory cloth. If you are afraid to do this, Lee will supply you with an undersized mandrell polished to your specs for a very reasonable fee.


  3. 7 loader

    7 loader Well-Known Member

    Oct 9, 2009
    Ahmen on the lockrings. I love my lee neck sizer, hated the lockring.
  4. joe0121

    joe0121 Well-Known Member

    Jul 29, 2010
    For what it's worth I just leave my dies in the little adapter for the press so I set them up and never screw them out I just take them out die holder and all.
  5. boomtube

    boomtube Well-Known Member

    Oct 8, 2007
    What gets called "neck tension" is not tension at all, it's usually just a difference in the diameter of a bullet and the neck hole. The lowest bullet grip we can obtain that still holds the cartridge securely is best for runout and accuracy. Controlling ignition start pressure is best done by adjusting bullet jump to the lands (aka, OAL) not agonizing over 'neck tension'. How tightly the bullet grip actually is depends more on the hardness of the brass than the differences in neck diameter.

    A smallish neck hole IS more difficult to seat bullets into but if you mic the neck of a loaded round and then mike it again after pulling the bullet you will see that the neck only shrinks back about 1 thou, the rest of the original difference simply got permantely stretched and only the last thou actually holds the bullets in place. Fact is, a high "tension" effort forces most bullets to cock on intial seating and contributes to bullet runout; runout is NOT good for accuracy. Years ago, after using my first collet neck die I got more and retired all of my conventional neck dies.

    Lee's collet die mandral is sized to produce a thou or so smaller neck on MOST cases but that can easily become different as we size and fire the cases repeatedly; hard brass springs back more after sizing. Some people (wrongly in my opinion) seek smaller necks by sanding down the mandral but annealing case necks is a much better method of controlling the finished neck diameter than grinding on the mandral.

    There is no point in putting a lot of ram pressure on a case in Lee's collet die. The brass is soft and swages down easily. Necks cannot be made smaller than the mandrel allows and it does't take a lot of pressure to reduce the fit to as small as can be done. Excessive pressure will first swage visible but harmless longitudial lines in the necks and, if the pressure is continued, the top of the die will strip and pop out. That soft aluminium top cap is made to serve as a safety feature to prevent the ham-fisted from damaging their die body or press.

    Lee's die, nor any other, can't make good necks out of bad necks, all it can do is avoid making the necks worse. And no seater from any maker or at any cost can seat straight ammo in bad necks.