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357 Sig Shoulder setback

Discussion in 'Reloading' started by ds7br, Aug 9, 2012.

  1. ds7br

    ds7br

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    May 10, 2012
    For those of you loading the 357 Sig how far back from fired dimensions do set the shoulder back? Thanks,
    Dennis
     
  2. F106 Fan

    F106 Fan

    8,033
    268
    Oct 19, 2011
    I don't shoot the .357 Sig but the process is no different than what might be done for .223 or .308. For autoloaders, the brass is sized to minimum. Normally, if you set the sizing die down until it touches the shell plate (and perhaps a little more so that the press cams over very slightly), the brass will be properly sized.

    You can always check with a case gauge.
    http://www.dillonprecision.com/content/p/9/pid/25549/catid/3

    Percision rifle is a different story. The case is not resized and the shoulder isn't bumped. Only the neck is resized to provide the proper tension for the bullet.

    Richard
     


  3. fredj338

    fredj338

    21,672
    901
    Dec 22, 2004
    so.cal.
    It depends on your gun. Use your removed bbl, size a case, drop it in. If it sticks above the hood, it's too long. If it sits below the hood, it's too short. Too long isa problem, too short not as much. You could get a misfire, but the extractor should hold the case in place.
     
    Last edited: Aug 9, 2012
  4. sig357fan

    sig357fan

    938
    71
    Apr 8, 2008
    SW OH
    use your barrel as a gauge, if a loaded round drops in the barrel when held chamber up and is flush or just below flush with the barrel hood you should be GTG.

    inverting the barrel (chamber facing down) while the round is still in the chamber should result in the round dropping freely from the chamber.

    also check funtion through your mag, I've found that the 357 Sig has a more tight spec on COL for proper feeding.

    sdig357fan
     
  5. Three-Five-Seven

    Three-Five-Seven Señor Mombo Millennium Member

    2,727
    34
    Aug 8, 1999
    Great Southwest
    Get some various factory rounds (Hornady, Speer, Winchester, etc.).

    With the barrel out of your gun, use a straight edge and feeler gauges to observe the amount of headspace that factory rounds provide with the setbacks they use.

    You'll see very quickly that there is a wide range and most use a generous amount of headspace -- most likely in an effort to accommodate dirt building up in the gun's chamber.

    Assuming you clean your gun regularly, you can cut the amount of headspace in half of what factory rounds employ. I use an headspace of 3 to 4 one thousandths. That works great in a clean chamber and will run without problems for a long range session.

    One of the other virtues of a bottle neck design is that blowback is minimized in the chamber, keeping it clean for higher round counts between cleaning.

    In other words, I have no idea why factories use such generous headspace in this round. Your pistol's chamber will tell you immediately how much headspace to use.
     
  6. dkf

    dkf

    5,433
    125
    Aug 6, 2010
    Lee .357sig sizer die with the die set tight to the shell plate and taking out any slack.(with the ram up) I was thinking about picking up another sig sizing die and shortening the length and rechamfering the mouth. I got some of those 100gr frang bullets from Midway and the profile sucks for .357sig so the neck set back should help for those bullets.

    Some .357sig brass is quite a bit longer than others.
     
    Last edited: Aug 9, 2012
  7. F106 Fan

    F106 Fan

    8,033
    268
    Oct 19, 2011
    Are you thinking about moving the shoulder back? That's not going to work. The cartridge headspaces on the shoulder, not the case mouth.

    Richard
     
  8. _The_Shadow

    _The_Shadow Ret. Fireman

    4,519
    21
    Jul 23, 2007
    Southeast, LoUiSiAna
    The 357Sig needs to be from flush with the chamber hood 0.000" but within - 0.004", if there is too much set back you could see neck seperations due to the excess working of the case neck area. Cartridges which are too short will experience light primer strikes or failure to fire!

    Some bullets with the olgive too low may not hold firm with the crimp...
     
  9. dkf

    dkf

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    Aug 6, 2010
    It head spaces on the case mouth. The whole idea is to bump the shoulder back a little and make more straight section of the neck to to try and get more neck tension on the crap profile bullets. Just an idea I thought I would try.
     
    Last edited: Aug 9, 2012
  10. F106 Fan

    F106 Fan

    8,033
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    Oct 19, 2011
    I stand corrected (yet again!), it does headspace off the case mouth unlike other bottleneck cartridges. Since that's the case, there shouldn't be very much variation in length. The spec is 0.885" - 0.010"

    The tolerance on neck location, AFAICT, is -0.005" so I still don't think you can bump it enough to do any good. You will just wind up overworking the brass in the area of the shoulder.

    But, hey, it might work! :embarassed:

    Richard
     
    Last edited: Aug 9, 2012
  11. dkf

    dkf

    5,433
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    Aug 6, 2010
    There has been sources over the years that said .357sig head spaces off the shoulder so it just added to the confusion.

    Thinking more after I posted I think I will just buy another shellholder or two and face it off as shellholders are cheaper than sizing dies. I think bumping it back further may work and with mild range loads the brass should probably last a while. I just need to find some time to do some tinkering.
     
  12. fredj338

    fredj338

    21,672
    901
    Dec 22, 2004
    so.cal.
    Not really. I know the books say so, but long before anyone wrote about reloading 357sig, guys were necking down 40 cases to reload & they were way short, no possible way to headspace on the case mouth. Get the shoulder wrong & you will have problems, it does headspace on the tiny shoulder.:dunno:
     
  13. dkf

    dkf

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    Aug 6, 2010
    The SAAMI drawing shows the dimension from the head to the case mouth (OAL of brass .865 +.000 -.010") marked as the headspace dimension.(designated by a circle with the X in it)

    What you said with the necked .40 brass makes sense. The necked down .40 brass is well short of SAAMI spec for .357sig though. Sort of seems like something simple that was complicated somewhere down the line.
     
  14. Three-Five-Seven

    Three-Five-Seven Señor Mombo Millennium Member

    2,727
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    Aug 8, 1999
    Great Southwest
  15. ds7br

    ds7br

    33
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    May 10, 2012
    Thanks guys,
    My die is set up to set the shoulder back .003 from the fired length. Trying 3 different factory loads gave 3 different measurements so I decide to size like do for my competion rifles; off the datum line on a fired case shoulder. I'm level with the hood end at .003 setback so should good to go.
    Dennis
     
  16. Three-Five-Seven

    Three-Five-Seven Señor Mombo Millennium Member

    2,727
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    Aug 8, 1999
    Great Southwest
    Correct !