how much neck tension is too much?

Discussion in 'Reloading' started by orch, May 15, 2012.

  1. orch

    orch Well-Known Member

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    looking for some imput....

    trying to reduce my case neck runout on my 25-06 Ackley... i know i shouldnt have even started looking at case neck and bullet runout :rolleyes: because this gun was and still is shooting awsome even before i started checking it... but knowing it is there just bugs me

    long story short, i'm running my brass through my redding die set... i have the full length and neck sizer die set as well as the conventional seater die for it.... i'm running 30-06 lapua brass necked down to 25-06 and have turned the necks with the rcbs system that reams the inside of the neck at the same time you trim the outer neck... the brass is then fireformed in the ackley...

    the fired brass always comes out of the chamber with a concentricity of 0.001" or less with most of them in the <0.0005" range (ie: the needle barely moves as i spin the brass in the concentricity guage)

    after sizing in either die i was getting concentricity readings in the neck of any where from 0.001" in some of the brass but in a lot i was getting .004"+ deflection... removed the neck sizer button and low and behold readings back in the < 0.001" range...

    i have tried letting the decapping pin/neck sizing rod free-float, i have locked it in while it drags through the neck of a perfectly concentric peice of brass, i have pollished the sizing button with 600 grit sand paper, i have run the button up as high as possible in die right below the shoulder, and have just switched to one of the redding free floating carbide buttons... neck run out still in the 0.004"+ range on most of my brass..

    if i just run this stuff through my dies without the expander button in, the necks are about 0.008" smaller diameter then when the neck expander is in...

    my question is: if i just seat the bullets in the non neck expanded brass is this gonna cause me more greif because the neck tension is too high?


    any help would be appreciated

    thanks, orch
     

  2. rscott5028

    rscott5028 Well-Known Member

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    Neck tension is more a function of the neck wall thickness and annealing.

    .008" won't make any difference. The bullet will become the expander button. So, you'll get the same tension as you would if the necks were .001" rather than .008" smaller than your bullet.

    The solution would be to use a properly adjusted collet die, or bushing die, or custom die.

    After sizing, you'd like the ID of the neck to be .001-.002" smaller than the bullet OD. Smaller ID is just over-working your brass. And, the same size as the bullet is not good.

    -- richard
     

  3. Mikecr

    Mikecr Well-Known Member

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    You're turning the necks with junk, and way oversizing.
    And the problem with so much seating force will be inconsistent seating depths, and probably bullet nose damage.
     
  4. green 788

    green 788 Well-Known Member

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    if you can't pull a bullet with an impact puller... that's too much. :)
     
  5. orch

    orch Well-Known Member

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    so.... basically... use the bullet as the expander while i wait lord knows how long to get a 25-06ai bushing die up here in kanuckistan....

    dont worry i know the aforementioned neck turning device is junk... again kanuckistan... it was the only one i could find at any of local places around here...
    and for the insane price they charged me for junk I hesitate on buying a new one especially after the 100 pieces of brass i originally turned with it have lasted me over 10 loadings and are still going strong... maybe when i need to get a new lot of brass i'll splurge and upgrade my neck turner...
    any recommendations on a neck turner?

    i anneal regularly and haven't had any cracked necks so it appears that has been mitigating the overworking of the brass...

    as for the bullet noses they don't contact the seater plug so seating depth inconsistency is the only thing i will have to check....
    that and if a kinetic bullet puller will work to pull a bullet :D

    thanks guys

    orch
     
  6. rscott5028

    rscott5028 Well-Known Member

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    I wasn't advocating that you *should* use the bullet as the expander. ...just saying that's the effect. It really doesn't have much to do with neck tension.

    To Mikecr's point, it's not going to do you any favors with respect to concentricity and consistent seating depth.

    Perhaps some Redding dry neck lube on the case necks will help with the expander button?

    -- richard
     
  7. RTK

    RTK Well-Known Member

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    How much does a little neck run-out affect groups really??
     
  8. orch

    orch Well-Known Member

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    yarghhh.. :D

    point taken....

    i did try neck lube too to no avail..... both dry and the sizing wax (at different times of course)

    as to RTK's question... i'm not sure it really does in this gun... the best groups i've every shot at 1000 yrds was with this gun. only problem is i wasnt measuring runout at that time and have no idea if the ammo at that time was consistently concentric or not....
    my groups have been pretty good recently since i started checking bullet and neck run out for this ammo but i have had the odd flier and i would love to blame it on runout and not just the shooter :D

    maybe i should never have measured it, ignorance is bliss...
    but when i'm shooting against my buddies at 1000 yrds for who buys breakfast i want to make sure i can rule out all of the variables....

    orch
     
  9. RTK

    RTK Well-Known Member

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    Only thing really important is that you don't have to buy breakfast:)