Bumping shoulder necessary?

Nessal

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Is bumping the shoulder back approx 0.002 really necessary? I mean, if you have no problems loading or extracting, it just sounds like another step that slows down the loading process. Also wouldn't setting the shoulder back work the brass more than just neck sizing and calling it quits?

The reason I ask is because I have been bumping the shoulders back for a while but then stopped a few months ago and have not experienced anything negative. All my rounds feed and extract as if they were bumped back. I noticed no difference....


Btw, I'm not full length sizing, just neck sizing now.
 

427Cobra

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    Re: Bumping shoulder necessary?

    I Full Length resize everytime, .001 bump is all that's needed, and since I only use Redding Type S dies the neck is resized at the sametime, so there is no extra work envolved.
     

    MitchAlsup

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    Re: Bumping shoulder necessary?

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Nessal</div><div class="ubbcode-body">Is bumping the shoulder back approx 0.002 really necessary? </div></div>

    Every once in a while, yes; all the time, no.

    Every firing cycle, the brass expands out to the limits of the chamber, indeed, even the steel chamber expands a triffling before snapping back. As the pressure reduces, the brass snaps back to close to its original size. The key word is close. So, the case slowly expands, longitudinally and radially.

    Eary in their life, the brass is more springy, and you might get 7-10 firings before you ned to squeeze the body back to size. Later you might only get 2-3. If you keep careful notes, you can almost see when the case is done and becomming a liability concern.

    Sizing dies push the sholder back, but also and just as importantly squeeze on the case near the web where the chamber is widest. A case that is too big at the waist won't go in the chamber any better than a case with its sholders up to high. And note, when the base of the case gets squeezed, the sholder will move forward! so you always need a die with a sholder when you squeeze the base. A die with only sholder and base is commonly known as a body die.
     

    Nessal

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    Re: Bumping shoulder necessary?

    Makes sense. I guess I'll wait till they get hard to chamber before I bump.
     

    JRose

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    Re: Bumping shoulder necessary?

    Necessary, no. I have 6 firings on some Lapua brass that only gets neck sized with no trouble chambering, or ill affects to accuracy.

    I do have to segregate my brass though, if I'm only neck sizing.

    Also, this doesn't hold true for autoloaders...
     

    rman1

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    Re: Bumping shoulder necessary?

    Not to hijack, but a realavent question. When you neck size only, with a bushing die, how much of the neck do you size? Half? More? Less? I've been having trouble with velocity spread, and I think this is the issue?

    Thanks.

    R.
     

    Dogtown

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    Re: Bumping shoulder necessary?

    Much of this will depend on your chamber specs. For autoloaders it's recommended that you FL size every time. Most bolt guns only need it every few firings, neck sizing between FL sizing. The only problem is when you get a match chamber made to tighter specs. In that case you will likely find that neck sizing alone will lead to sticky bolt in short order.