Belted Magnums--Headspace on Shoulder or Belt?

Discussion in 'Reloading' started by MSLRHunter, Jul 20, 2010.

  1. MSLRHunter

    MSLRHunter Well-Known Member

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    Do most of you guys that load for belted mags prefer to headspace off of the belt or the shoulder? I load for 2 belted mags, 7mmRem and 300Win, and set the shoulders back 2-3 thou with good results and good brass life. In order for them to headspace off of the belt, the shoulders would have to be set back much farther than that right?
     
  2. woods

    woods Well-Known Member

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    It would depend upon what headspace you had at the belt.

    IOW a belted magnum might have .005" headspace on a new case which is the dimension between the front of the belt and the recess in the chamber it will bear against. But that same case may have .020" between the new case shoulder and the chamber shoulder. Then after firing you would have to push the shoulder back .006" or more to have it headspace on the belt again.

    But if your chamber has a headspace of .001" which, again, is the distance from the front of the belt to the recess in the chamber against which the belt will stop forward movement, then after firing you would only have to push the shoulder back .002" to have the belt again act as the headspacing agent.

    Now all of this will vary with different makes of brass and chambers.
     

  3. phorwath

    phorwath Well-Known Member

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    Off the shoulder.
     
  4. Buffalobob

    Buffalobob Writers Guild

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    If you have a custom chamber that is set to head space off the belt then use the belt. If your chamber and/or brass is sloppy then you should use the shoulder.
     
  5. boomtube

    boomtube Well-Known Member

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    Headspace for a reloader is NOT the same consideration as a gunsmith doing the chambering. WE want the cartridge to fit in that chamber with as little slop as possible.

    That means we work with the shoulder for any bottle neck case, neither we or our ammo care where the belt is; you are doing good.
     
  6. Rustystud

    Rustystud Well-Known Member

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    Belted magnums all headspace off the belt. The headspacing gauges don't extend to the shoulder area of the case. Headspacing off a case shoulder may leave you with a unsupported area in front of the case belt in the web area and thus allow a catistophic failure.

    Nat Lambeth
     
  7. BobbyL

    BobbyL Well-Known Member

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    Agreed. Always head space off the belt. If there is something wrong then its in the brass/dies or the reamer. I have cut dies to allow for extra shoulder bump and that usually fixes the problems. If its long then you need to form the brass to that chamber and start all over.
     
  8. boomtube

    boomtube Well-Known Member

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    "Headspacing off a case shoulder may leave you with a unsupported area in front of the case belt in the web area and thus allow a catistophic failure. "

    That's hilarious! You are joking, right? :D

    MSLR, if a cartridge chambers snugly, belted, rimmed or neither, it's all as well supported as is possible to obtain and there is MUCH less hazard of a head seperation too. We aren't resizing to match the steel headspace gages gunsmiths use to cut a chamber, we are loading our own brass cases. For some 40+ years, I and every magnum reloader I know of has FL sized thousands of cases to fit the shoulders to the chamber. Guess how many "catistrophic failure" events we've experienced!!! :rolleyes:
     
    Last edited: Jul 21, 2010
  9. BobbyL

    BobbyL Well-Known Member

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    I believe they are talking about the chambering not the brass. I could be wrong though. Wouldn't be the first time....

    bobby
     
  10. 7 loader

    7 loader Well-Known Member

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    The original idea behind the belt was for head space. But if your case life is good, of the shoulder is fine.
     
  11. BountyHunter

    BountyHunter Writers Guild

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    Last edited: Jul 21, 2010
  12. boomtube

    boomtube Well-Known Member

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    "The original idea behind the belt was for head space."

    7, you're correct of course. It started with long, slender H&H magnums which had very slight shoulders that needed help to chamber and not be driven too far forward by the pin strike and primer concussion. The belt was simply a variation of a rimmed case and it worked well enough. In many peoples minds the belt soon became the meaning of "magnum" but that really wasn't true, as proven in more recent years by beltless magnums.

    Most rifle magnums were and remain remain bottle neck cases. A competent handloader will avoid setting the shoulders back any more than is absolutely neccessary in order to avoid potentially dangerous head seperations.
     
  13. MSLRHunter

    MSLRHunter Well-Known Member

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    No, I was asking about sizing brass to headspace off the shoulder or belt. I had several local people tell me that you must always size your brass so that they headspace off the belt, and I politely disagreed. Just wanted to see what some of our resident experts here do. Thanks for the responses, I will continue doing what I am doing with minimally bumping those shoulders back.
     
  14. BobbyL

    BobbyL Well-Known Member

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    Understood. Yes if you fire the case in the chamber and it forms nicely a minimal bump of about .002 is usually perfect. Some of the magnums like a little more but depends on the gun. All you would need is what we call gizmos which are that last inch of the barrel we cut off when we chamber and run the chamber reamer in it enough to get the shoulder. Its a very handy tool when you are reloading.

    bobby