How do you control neck tension?

Discussion in 'Reloading' started by bookworm, May 25, 2010.

  1. bookworm

    bookworm Well-Known Member

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    How do you control neck tension under a variety of sizing methods?

    It makes sense to me that when using a full length die with expander ball (RCBS), that neck tension should be consistent. However, using this setup how do you reduce neck tension?

    I've read that you can get good results by using FL sizing w/o the expander ball. With that method, how do you control neck tension? If you bump the shoulder back by a couple thou or so, does that tighten the neck tension...and is that how you control it?

    How about neck sizing? Same as above?
     
  2. woods

    woods Well-Known Member

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    The way you control neck tension or bullet grip by sizing without the expander ball is to outside turn your neck thickness. For example, if you are sizing for a 30-06 and:

    Your neck thickness is .014"
    Your sizing die sizes the neck down to .330"
    You want .002" bullet grip

    then the math would be

    caliber - bullet grip = desired ID of neck .......... .308" - .002" = .306"
    die dimension - desired ID of neck = total brass thickness ........... .330" - .306" = .024"
    total brass thickness / 2 = thickness each side ............. .024" / 2 = .012"

    So if you outside neck turned your brass to .012" then you could size your brass without the expander ball and have .002" bullet grip .............. theoretically

    I say theoretically because there are some other variables that will have some effect, namely springback which is a function of the softness or work hardening of your brass neck and how accurately you can outside neck turn to an exact .012".

    If you really want to get exact then it helps to have an accurate way to gauge the ID of the neck. I use pin gauges
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    they measure to the .001" but you can tell additional information by how easily or difficult the pin gauge goes in.

    IMO bullet grip is also affected by the condition of the inside of your neck. IOW any scratches, burrs, left over lube etc. will also affect bullet release and seating depth variances. To solve this problem I use scotchbrite and mica
    [​IMG]
    [​IMG]
    [​IMG]

    I recently did a test where I size with 3 methods on 5 case each and gauged the resulting bullet grip.

    Regular sizing die with expander ball
    Bushing style Redding neck sizer
    Lee Collet Neck Sizer

    Using the pin gauges and to the best of my abilities, I came up with the following conclusions

    The Lee Collet had the exact same ID throughout the 5 cases. IOW the same pin gauge went in with the exact same resistance.

    The expander ball did almost as well using the same pin gauge but with varying resistance.

    The bushing neck sizer varied between three pins with it tight on one side and loose on the other side of the center pin size. These case necks were outside neck turned to the best of my ability.

    Lots of ways to skin this cat but doing it this way my velocity extreme spreads have mostly dropped to the single digits and my groups have shrunk at the longer distances.

    YMMV
     

  3. TOM H

    TOM H Well-Known Member

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    Myself I use bushing dies and if you get the redding type S dies you get a standard type expander also what called a Pin Retainer that allows bushing to set neck tension.
    Type S Bushing Dies | Redding Reloading Equipment: reloading equipment for rifles, handguns, pistols, revolvers and SAECO bullet casting equipment
     
  4. boomtube

    boomtube Well-Known Member

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    The meaning of the first two posts is that you can't control it with standard dies, there is no such adjustment.

    Use Lee Collet neck dies, they will take care of all the variables as well as it can be done and without any fuss.

    If you wish to do a shoulder bump, get a body die OR bore out the neck of a FL die a few thou over max so it won't make neck contact.

    There is no benefit in more than 1 to 1.5 thou of "bullet tension" (an interferrence fit actually), any more will only increase run-out.
     
  5. Mikecr

    Mikecr Well-Known Member

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    I use bushing neck dies(Wilson or JLC).
    My 'tension'(or as mentioned 'interference') is set at .001" after springback.
    For 'grip amount on bearing', which is a release force variance, I adjust via partial sizing.
    I've chosen a convenient starting standard here as 1cal, and it's turned out very well. That is, I neck size to ~.22" down the neck from it's mouth for 22cal bullets, .26" for 26cal bullets.
    I can adjust this easily with these dies(for load development) one way or another.

    After sizing a batch of necks, I run each through a seating force gauge of mandrel design to verify all will actually seat with the same force(a force chosen during load development). For any that don't, I set aside to stress relieve in another batch.

    It doesn't make sense to size the entire necks, just because it can be done. Especially when bullet bearing doesn't even reach so deep! Such action is not only bad for brass life, it likely reduces performance potential from a load.
     
  6. Boss Hoss

    Boss Hoss Well-Known Member

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    I have my dies made (bushing type) when the rifle is made. Good stuff above but do not forget--------Never Mix brass that has been fired 5 times let’s say with brass that has been once fired. The more brass is worked without being annealed the less “spring back” consistency there is which translates to inconsistent neck tensions if you are mixing brass.

    Also when going to shoot a 1K event I will always load the night before to ensure a "fresh" set in the case. A trick I learned from Speedy Gonzalez and Rich Machholz at Sierra who I shoot with.
     
    Last edited: May 26, 2010
  7. Mikecr

    Mikecr Well-Known Member

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    Boss, I hope you didin't get 'less annealing = less springback' from them..
    If so, they've sent you snipe hunting!

    Annealing doesn't restore tension, it relieves excess.
    Well, technically 'annealing' ruins brass. It's 'stress relieving' that we do.
     
  8. Boss Hoss

    Boss Hoss Well-Known Member

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    Mike------NO NO NO-----a case that has been loaded and fired 5 times will hold the case differently than a new or once fired one. The more brass is work hardened the less “set” it will take when sized. So if eventually you will have to either anneal or use the next size down on the sizing bushings (is a pain tried it years ago).

    Have gotten to anneal a few cases lol and if the Lapua Brass was not so expensive and a pain to turn then I would just throw it away after 5 firings. Have a few bags I am going to take with me when I go see my buddy that has this machine that rotates with burners on each side of the case. Forgot the name of it @#$()@$%*(!@$!!!!!!
     
    Last edited: May 26, 2010
  9. tom m.

    tom m. Well-Known Member

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    boss,
    mike is right. notice he said .001 AFTER springback, and then adjust to what he wants with a smaller bushing. this works, this works really well i might say. you are correct, you can NOT get your neck tension back by annealing. it will not happen, BUT you can, and i do, anneal to get the necks and shoulder softened back up. BUT, you still MIGHT need a smaller bushing then you did when the brass was fresh. annealing does indeed help you get the shoulder bumped back consistently, but it absolutely will not restore neck tension to that of fresh sticks. it also helps you get the "seal" back, ever notice older brass getting soot clear down on the shoulder, annealing should help this.
    tom
     
    Last edited: May 26, 2010
  10. TOM H

    TOM H Well-Known Member

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    I've been using the Wilson,Neil Jones bushing dies since the 80's. They don't use expanders and just size part of the neck so that is all that gets works if you want alittle more or less tension change bushing size.

    I use a body die for sizing when needed and tell the true I don't anneal or plan on starting. One time I figure out cost on new case how many reloads before the case cost nothing to reload most time I get to that point so doesn't bother me to replace that brass.


    I load about my first 15yrs with standard type dies and I'm sure if I was still using them I may do things different.
     
  11. Loner

    Loner Well-Known Member

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    You sure do regain neck tension after annealing. I have annealed range brass so hard
    after sizing it would not hold a bullet at all. After annealing and back through the sizer it would.
     
  12. Mikecr

    Mikecr Well-Known Member

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    Loner,
    When I said "Annealing doesn't restore tension, it relieves excess", I should have said simply that 'annealing relieves excess springback'. Actual tension produced is relative to your conditions.
    As with anything there are atleast two sides, with extremes..

    In your example, excess springback from many-sized necks is reducing bullet grip. The brass is so hard that sizing will not take. So annealing reduces the springback to a point where there remains enough bullet grip after sizing.
    But annealing will not always increase 'tension' (bullet grip). If the brass is not excessively hard at the time of annealing, then it will lose tension with annealing. In fact it can lose so much from annealing that it will not hold a bullet from one sizing.

    This is balancing of context regarding 'tension' (bullet grip), and springback (hardness).
    Springback is flat out reduced by annealing.
    Tension left from annealing is either improved or worsened. Depends on your conditions..
     
  13. boomtube

    boomtube Well-Known Member

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    Mike, good explaination. I wanted to say that but was too lazy! :D
     
  14. Len Backus

    Len Backus Administrator Staff Member

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