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Explaining Headspace

Discussion in 'The Ammo & Reloading Forum' started by Insulation Tim, Jun 6, 2010.

  1. CampingJosh

    CampingJosh Moderator

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    Edward, that's a great graphic! Thanks for adding to the thread.
  2. Edward Horton

    Edward Horton New Member

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    For you Enfield collectors and shooters. ;)

    Its not the headspace that gets you, its actually the "HEAD CLEARANCE" or the air space between the bolt face and the rear of the case that causes your cases to stretch. This applies to any type case, rimmed, rimless, belted etc.

    [​IMG]

    [​IMG]

    Many people blame the Enfield rifle for short case life, the real problem is American commercial factory cases are not made to British military specifications. If any cartridge case is properly fire formed with the base of the case against the bolt face it will last much longer.
  3. madbuck22

    madbuck22 Member

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    this might be a stupid ? how do u get the original head space back from your fired round is it when u put it through the re sizing die? or when u trim?
  4. CampingJosh

    CampingJosh Moderator

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    No stupid questions, madbuck. We were all new at some point, and for some of us (me in particular) it was more recent than others.

    Resizing a case will return it to the original exterior dimensions as though it had not been fired. This should cause the case to headspace correctly no matter how it does so (on the rim, the belt, the shoulder, etc.). However, if a case is too long, that case or a bullet seated into that case can cause problems with headspacing (among other possible issues).

    So really, you need to both size and trim (if over max length) to make sure that previously fired cartridges be safe to use again.

    Clear as mud yet? :D
  5. madbuck22

    madbuck22 Member

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  6. Edward Horton

    Edward Horton New Member

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    On a bolt action rifle you only need to push the shoulder back .001 to .002 when full length resizing.

    A full length resizing die is designed to push the shoulder back .002 shorter than minimum headspace. If your actual headspace is .003 more than minimum headspace and you die is set up to make hard contact with the shell holder you will be pushing the shoulder back .005 or more. This will cause case head separations and short case life and could als effect accuracy.

    Below simple ways to control and measure cartridge headspace.

    [​IMG]

    [​IMG]

    [​IMG]
  7. mw0248

    mw0248 New Member

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    you guys need a little coaching here;
    I'm talking about RIFLE rounds, but the same kinetic principle aplies to pistol, and revolver cartridges as well;
    When the bolt of your rifle is locked, there is a 'head space', that distance between the back end of your round, and the bolt; Usually around .001-.002 of an inch;
    When your round fires, the PRIMER actually moves back, and hits the bolt face;due to the round (the brass) expanding into the chamber dimensions of your rifle; a gas seal is formed when your brass expands into your chamber, and gess what? The only thing that can move is your PRIMER; and the bullet; The primer hits the bolt face, and sits there, waiting for the shell ( the brass) to decompress as the bullet goes down the barrel, and the PRIMER actually re-seats its self back into the spent shell;
    This is what headspace is about; Too little headspace can't be measured; simply because, if your round wont chamber, it's not a headspace problem; It's a chamber broblem;
    On the other hand, if you have a firearm that is shot out (neck/shoulder), this will allow
    the unfired round to travel too far forward, thus creating a "HEADSPACE" problem, cause it allows the PRIMER to go too far back, allowing gases to escape behind the back of the brass case that you are shooting; This causes all kinds of problems, some of which can cause injury/death if not taken care of;

    To an upcoming shooter, HEADSPACE can be confusing, but its just physics;

    If you shoot a lot like I do, then you find these things out;

    Lot easier now, than when we tried em out;

    By the way, I have a SUPER .243 load with 95 gr. if you are interested (bulls eye at 200 yds);
    Shoot well, and be safe!!
    Mike
  8. mw0248

    mw0248 New Member

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    when you 'full length' resize a shell, you stretch the shell FORWARD, cause thats the only way it can go; the brass thins as is it stretched and gets longer, causing it to get thin; then you get split cases, due to pressure more than the thin case can take; and you also end up trimming them for being too long;

    The above mostly applies to autoloaders;

    If you shoot a bolt action, or lever action rifle, dont full length re-size your cases;

    just collet size them for the neck size of the round you are shooting; you have a perfectly sized shell for your rifle; and your cases will last ten times longer;

    From LEE 2ND EDITION RELOADING MANUAL
  9. passagenight

    passagenight New Member

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    Ok, understood; I think...but I have a Marlin 1895 and a Ruger #1 both chambered for the 45/70. I reload, and have done so safely so far. These are rimmed cases of course which would define the headspace as being almost immaterial?.......but some rounds will chamber in the Marlin and will not chamber in the Ruger. The difference seems to be the 'taper' of the bullets used. If tapered the Ruger will chamber; if 'rounded' it hangs up just in front of the rim. Of course I don't force this.
    Is this a case where the bullet is engaging the rifleing of the barrel on it's curvature?
  10. howlnmad

    howlnmad Well-Known Member

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    It sure sounds like that's your problem. Are you seeing marks from the rifling on the round nose bullets?
  11. scansat

    scansat New Member

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    Excellent explanation. I've always wanted a more detailed explanation and this thread hit the nail right on the head!
  12. mgrove4758

    mgrove4758 New Member

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  13. BlackEagle

    BlackEagle Well-Known Member Supporting Member

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    Welcome to the forum, mgrove. You've found a great place to listen, learn, and hang out and chat and laugh.

    What do you shoot?

    Are you into reloading?
  14. howlnmad

    howlnmad Well-Known Member

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    Those shims in post #36 look like a great idea but you can acomplish the same thing with a set of feeler gauges.
  15. oneidapj

    oneidapj New Member

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    I am just about ready to load my first,,, I think. Something always comes up new that I need to know more about before I start. Now I am waiting to get a case re-sizer because all the brass I have collected over the years (shot only once, some twice) are different length, from 2.484 to 3.000 and the Nosler book says max is 2.494. Now mw0428 says we don't need to length size them??? We both have bolt action 30-06. Mine is a very old BSA? and hers is new Mossberg.

    For myself I bought Nosler partition spitzer 180 grain and my wife Hornady 165 grain sst (which has the groove around the bullet, the Nosler one doesn't). Do these need some kind of crimp? If they do then the instruction are to re-size all brass to the same length. And if length is know big deal won't the mouth of the brass at some point stretch enough to hit a step in the barrel?

    One more question is- should I keep my brass seperate form my wifes' in the future for reloading?

    Dennis
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