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  1. #31
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    Default Re: Headspace measurement

    Thanks, I'm on the same page.

  2. #32
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    Default Re: Headspace measurement

    By re-sizing the case is shrunk in width, but - as a result - will grow in length. Effectively the shoulder is pushed forward with full length sizing, untill it (eventually) reaches the die's shoulder. From hereon, you can push the shoulder back if you so wish. Careful measurement will tell you when that starts to happen, and how much is too much. Never - never ever - trust the "shellholder touching the die on the ram's upstroke".

    The shell's shoulder dimensions have a massive effect on accuracy - and dramatically affects how the case will suffer in the chamber - much more so than case overall length. But, as 414 points out, don't let trim length get out of hand, as it wil create problems of its own volition.

  3. #33
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    Default Re: Headspace measurement

    Quote Originally Posted by 414gates View Post
    If you have partially sized the neck, you haven't touched the shoulder, and you have wasted your time. Either full length size, or neck size, but this partial neck Sizing is neither.
    ****************************************
    I am afraid I do not agree with this.
    There is a good place in reloading for partial neck sizing, especially partial that barely or just touch's the shoulder.

  4. #34
    User 414gates's Avatar
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    Default Re: Headspace measurement

    Quote Originally Posted by treeman View Post
    There is a good place in reloading for partial neck sizing, especially partial that barely or just touch's the shoulder.
    I don't get it.

    In all case sizing operations, the neck is always sized, it has to be, or you can't seat a bullet.

    Body sizing is optional, which is why we have neck sizing dies. [ Off on a tangent, neck sizing only is out of fashion ]

    Why run a case into a neck sizing die, but not all the way, so only part of the neck is sized ? Why mess with neck tension like that ?

    If you barely, or just touch the shoulder, the neck is sized - klaar, there's nothing partial there.

  5. #35
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    Default Re: Headspace measurement

    Lets see how far we agree.
    You can size with a full length die, but stop before shoulder starts, therefore not touching the shoulder, you will likely how ever see some die contact on case body.
    You can do above but touch the shoulder without bumping it back and full size neck and body, but no shoulder bump back.
    You can do above but go a fraction further down bumping shoulder back and full length sizing neck and body with a shoulder bump back. This is not necessary every reloading and works case a lot.

    I size down to about 1 or 2 mm from start of neck depending which caliber, avoid pushing shoulder back and have very little body sizing.
    I believe this works case less, gives enough neck tension and has the benefits of a fire formed to my chamber case.
    Bump shoulder back and full length size when camming over the bolt becomes tight.

  6. #36
    User 414gates's Avatar
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    Default Re: Headspace measurement

    Quote Originally Posted by treeman View Post
    I size down to about 1 or 2 mm from start of neck depending which caliber, avoid pushing shoulder back and have very little body sizing.
    I believe this works case less, gives enough neck tension and has the benefits of a fire formed to my chamber case.
    Bump shoulder back and full length size when camming over the bolt becomes tight.
    I understand. You are effectively neck sizing only using a full length die.

  7. #37
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    Default Re: Headspace measurement

    There's a big difference between bumping the shoulder back and full length sizing the case.
    Full length sizing will push the shoulder back to as close as possible to the SAAMI specs.
    But you don't have to fully push the shoulder all the way back to that point in a F/L die.
    There are many who say that you should always "bump" the shoulder back by 2 thou on a bolt gun and at least 4 thou on a semi.
    They argue that if you don't, the powerful camming action of closing the bolt will push the shoulder back anyway to fit the chamber, and you have very little control over how much it does that, in contrast to setting up your F/L die properly to achieve the 2 thou pushback ("bump"). Bear in mind that by using the F/L die to neck size only, without some pushback on the shoulder can cause your case to "banana" slightly that will cause concentricity issues because the case walls are not held sufficiently tight in the die.
    Neck size only dies have fallen out of favour because they don't push the shoulder back at all.
    That's my take on it.

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