How much neck tension

Discussion in 'Reloading' started by BillR, Sep 20, 2007.

  1. BillR

    BillR Well-Known Member

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    I had a chance to go antalope hunting today work ended up being a pita and had to pass. Would of been fun though. :(
    Anyway I ran into a problem while getting a load worked up for the .25-06AI. Its what I get for trying to make things so perfect I guess. Anyway here is the story.
    The gun has a tight neck chamber of .282 and I trimmed my necks to .011 to give the case .003 total neck clearance. Loaded cases chamber very easy. I ordered up a Redding S Type Bushing neck size die in .279. WRONG.
    What I ened up with is a case without enough neck tension to keep the bullets locked into the case. They can be slid up and down slightly in the case neck. Won't come out but they can move. Not a good situation I'm thinking. To fix the situation I went back thru my culls and found about 20 cases with a neck thickness of .012 that need to be turned down a bit more. They worked well and the bullet stays where its supposed to be. Gun shot very well into 1/2" and with some fine tuning of the load and optics will do much better.
    Now the question I have is this. How much neck clearance is necessary. Is .003 enough or too much. If its about right for clearance then how much neck tension should I give the case. Or did I miss something. Need to order a new bushing and I am wondering just what size to get.
     
  2. BountyHunter

    BountyHunter Writers Guild

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    Sounds like it could be either of two things.

    1. Your cases were turned to small for the bushing. Go one size smaller.

    2. Your cases are "work hardening" as you fire them and not actually squeezing down to the bushing diameter. Go one size smaller, but you really need to anneal the necks and shoulder.

    BH
     

  3. brianwinzor

    brianwinzor Well-Known Member

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    BillR, Sorry to hear about having to miss your hunting trip. I believe that BH has nailed it.

    Did you anneal your cases after fireforming? Cases will always spring back around 0005 after firing, and if they need annealing they sometimes spring back much more. (or maybe dont expand sufficiently on firing)

    A simple test which I always perform before reloading a fired case is to slide a bullet down into the neck, if the bullet passes freely, then the neck anneal is ok. However, if it is either partially or fully restricted then I put that case aside for annealing, which I find solves the problem.

    Only having .003 neck clearance, means that you have little margin for error in your reloading procedures.

    I have a similar problem to you in my .224 Clark. The chamber is .2543, and my loaded round is about .2520, (necks .014) so I only have about .0023 clearance. My RCBS neck sizing die only reduces the case necks to about .252 (or a tad less). So due to differences between cases, about 20% of my cases do not have enough tension to securely hold the bullet. However, if I full length size the case, the neck is reduced to .250, which is sufficient to secure the bullet on all cases. Rather than use my F/L die each time, I intend to purchase a Redding S Type with a .250 bushing.

    Once you get these minor problems, sorted out, I believe that you will love your 25/06AI. Good luck. Brian.
     
  4. BillR

    BillR Well-Known Member

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    The cases have all been annealed prior to fireforming. I then turned the necks and sorted them as to size. I had been advised that .003 was enough clearance for a loaded round. (Maybe bad advise) So when I ordered the bushing I figured that a .279 would hold the bullet. Didn't happen. The .257 bullet drops right down the neck. Won't come out easy but my collet bullet puller takes care of that without any major problem.
    Using the .012 neck cases from the culls worked out ok. Got the gun sighted in and everything working right with no extra presure signs and bullets staying where I had them seated, about .015 off the lands.
    I am going to take your advise and anneal them again though and see if the problem goes away. Can't hurt anything.
    I also was wondering if the neck expander would be removed after I went thru and resized all the brass and then run them thru again. Maybe that would give them enough neck tension. It has been fun playing with gun as I feel like a detictive. I keep finding things to investigate and lots of clues to problems. Its been a long road already but I will say this. I have NEVER had brass that was this uniform in every way and I don't know if its going to improve accuracy or not yet. Might not make the groups smaller but has to cut out some of the fliers a person gets.
     
  5. BountyHunter

    BountyHunter Writers Guild

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    Nothing is wrong with the .003 neck clearance. That is not the issue and has nothing to do with the problem.

    The problem is simply either the bushing is too small or the cases are work hardened.

    Now you said a .012 neck works fine. What is the loaded round difference between the .012 and the .011 rounds loaded? You will normally need about .003 smaller neck bushing than the loaded round. Plan on .001 springback so that gives you really .002 neck tension which is the critical factor.

    BH
     
  6. BillR

    BillR Well-Known Member

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    To get decent a decent neck tension of about .002 I'm going to have to go to a .277 bushing if I have this all figured out right. I'm ok with that. I'm also going to anneal all the cases again then resize them again just to see what happens. Maybe doing all the case prep work hardened them again.
     
  7. Eaglet

    Eaglet Well-Known Member

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    BillR,

    All your calculations were right. 0.279 is the dimension your neck will have once the bullet has been inserted having a 0.011 case neck thickness. Where you missed was in ordering the right Bushing neck size.
    Usually you want it between 0.001 and 0.003, as you can see, with the 0.012" neck thickness, that neck tension was able to hold the bullet.
    For hunting it's recommended to have 0.002" or 0.003 whichever gives you better accuracy. So, instead of ordering a bushing of 0.279" it should have been 0.277" and or a 0.276" then all would have been fine!
    Good Luck! :)
     
  8. TOM H

    TOM H Well-Known Member

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    Bill you did everything right and I won't anneal any cases. Only thing that wasn't allowed for was neck tension. You might of got enough neck tension with a neck thickness of .0115" as clearance is normally .002" when you increase that number to .003" you decrease your bushing size.

    neck thickness .023 .022 .024
    bullet dia .257 .257 .257

    total .280 .279 .281

    clearance .02 .278 .277 .279
     
  9. BillR

    BillR Well-Known Member

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    I guess I knew the answer all along its just that I couldn't belive I goofed that bad. Even had the Redding Rep working with me on figuring it . Just never figured on needing that much neck tension is all. OH well too much work and too little time hunting.