7mm STW-case splitting

Discussion in 'Reloading' started by Petersen, Apr 30, 2007.

  1. Petersen

    Petersen Well-Known Member

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    alright.. i have been shooting my STW for a while now without much trouble until today.

    a case split around the bottom of the case and when i looked at the other loaded rounds, they had "stress" marks in the same area so of course they would do the same if i fired them. the loads have been kept below maximum and this was only the fourth time the round was fired. the primer pockets have never blown out, the bolt has never been hard to open (ways that have usually let me know the load was too hot). ????

    i am wondering if it is just a bad batch of brass. i have shot my winchester brass around nine times with no problem (different load). i bought some federal factory rounds for the brass as i always heard that federal makes good brass and the selection for STW brass is very limited. i shot the factories, and then this is the third time reloading.

    bad brass... or the loads just too hot???

    any help or ideas is appreciated.
     

  2. 1doug

    1doug Well-Known Member

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    You should check your headspace.

    d-a
     

  3. Petersen

    Petersen Well-Known Member

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    head space is good. the rifle has a long throat and you can't even get close to the rifling without the rounds not fitting in the magazine. i am loading at the recommended overall length.. thanks.
     
  4. EddieHarren

    EddieHarren Well-Known Member

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    Overall length and seating depth have nothing to do with headspace. Since belted cases headspace on the belt, your FL die could be moving the shoulder back too far, resulting in case head separation. Measure a fired case from head to shoulder, then measure one after you have FL sized it. You may need to get ahold of a comparitor for a caliper or, have someone with a 7STW reamer make you a "Widget"
    I would discard all of your brass, from this batch, and start over with new brass, after you get your die set right.
     
  5. Ridge Runner

    Ridge Runner Well-Known Member

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    to set your die expand a stw case, or start with an 8mm RM brass, screw your die in till its 3/8's above the shellholder and resize, try it in your rifle, it shouldn't fit, now screw your die down a lil at a time until the bolt just closes with a lil resistance, then lock your die down, its now set to your chamber, and fed brass is thinner than most.
    JS
     
  6. Petersen

    Petersen Well-Known Member

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    i use the stoney point gauge and the shoulder is set back a few thousandths after the round is fire. (partial full length sizing). if federal brass is thinner i think that is the problem. i have had no problem with the winchester brass and the die hasn't been changed. thanks. tyler
     
  7. jwp475

    jwp475 Well-Known Member

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    If the split is a circumferential split then in my opion I agree with the post above that it is a head space problem.........
     
  8. blackco

    blackco Well-Known Member

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    +1 for DocEd!!! My dad had the same thing in a 300wm; circumfrencial (is that a word)cracks ahead of the case web, backed off the resizing die just a tiny bit and viola!!! extended case life.
     
  9. jwp475

    jwp475 Well-Known Member

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    [ QUOTE ]
    +1 for DocEd!!! My dad had the same thing in a 300wm; circumfrencial (is that a word)cracks ahead of the case web, backed off the resizing die just a tiny bit and viola!!! extended case life.

    [/ QUOTE ]

    Exactly..... /ubbthreads/images/graemlins/shocked.gif
     
  10. Freebore

    Freebore Well-Known Member

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    I get @ 6 loadings max out of my 7STW or my 308 Hammonds (same 8 mag case) . I've have a case seperate once trying to get more loadings. My shoulders are bumped .0015. I use Rem for the 308Hmnds and WW, Fed for the 7STW. I only shoot full house loads.
    If your getting 9 loadings your doing good!
     
  11. BigSkyGP

    BigSkyGP Well-Known Member

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    This is the reason I neck size my brass. Shooting, and full-sizing works the brass back and forth there just infront of the belt. There is also a longitudinal stretch when brass is fired, it happens to mostly stretch right there infront of the belt. Neck sizing helps reduce this streching and flexing, your brass will last longer.

    You can do mostly the same thing, like the guys before described, by backing off your FL sizing die.

    Hornady loading manual has a very good description, and illustrations for these efects.
     
  12. Petersen

    Petersen Well-Known Member

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    i have got the stw figured out now.. the federal brass went in the trash..

    the chamber was checked with gauges and it is fine. i only had the issues with the federal brass,

    the load i am shooting now is the 160 accubond at 3125 avg.. this shoots ragged hole groups. using 80 gr. h1000 and cci primers. the gun is a sako..

    thanks.
     
  13. BountyHunter

    BountyHunter Writers Guild

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    Peterson,

    there actually is no such thing as "partial full length sizing" unless you are using a custom die cut that way, which no one would waste the money on.

    You either do or do not FL size. Like being pregnant.

    What you described is the one and only correct way to FL size. :D

    With FL sizing the only issue is how much you push the shoulder back and you are spot on if you limit it to .002 max.

    NS is often a poor excuse for not learning how to set up dies and having ill fitting dies. Eventually, you have to body bump or FL size or throw the brass away, so why not learn how to do it right from the beginning. Proper dies set up correctly, do not cause separations or shorten case life. Old wives tail.

    Even the supposed ardent practioners of NS here, use body dies often custom fitted to their chamber. Which essentially means that they are FL sizing only doing it with two steps instead of one.

    BH
     
  14. Petersen

    Petersen Well-Known Member

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    thanks.. sounds like what i did is right as it is the same for most of my guns.. must just be some different terminology depending whose book or instructions your reading..

    my best guess for why i was getting the splitting around the belt is this. the federal brass were originally factory loads. the first firing weakened the brass as they didn't fit the chamber as well as needed. then they split on the next firing. if this isn't the case, then the brass was just no bueno..

    doesn't really matter as on my winchester brass i am on my 4th loading and having no issues at all and great velocity and accuracy.