Shoulder Bump Measurement Check

Discussion in 'Reloading' started by Michael J. Spangler, Jul 5, 2010.

  1. Michael J. Spangler

    Michael J. Spangler Well-Known Member

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    hey guys,

    i was wondering how much headspace slop is normal?

    i'm starting some more loads for the .330 rum. now that i have a few more measuring tools i wanted to go through all the steps to make sure i get the most out of my reloads.

    i determined my seating depth with my hornady OAL gauge. so i figured i would move on to the next step in precision reloading ; )

    now i've been reading in to my shoulder bump vs neck sizing. the last cases were neck sized, but the shoulder bump makes sense so i figured i would take some measurements.

    using the 420 headspace bushing from hornady i measure a fire formed case and came up with a measurement of 2.464" then i measure a FL sized case and came up with a measurement of 2.458"

    so there's only a .006" bump from fire formed to full length sized. is this a big difference?

    does this seem right? this is all pretty new to me and i don't have much reference to what the norm is. thanks for the help guys.

    by the time i figure this whole thing out i'll need a new barrel. damn 300 RUM
     
    Last edited: Jul 5, 2010
  2. winmagman

    winmagman Well-Known Member

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    Michael,

    Are you sure those numbers are correct? A case should not be .196 longer after having the shoulder bumped back.

    Chris
     

  3. nddodd

    nddodd Well-Known Member

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    I don't know much but it sounds to me like your full length die needs to be screwed down into the press a little more. I ran into this same problem a couple years back. If the die is out to far it will stretch the case.

    Hope this helps,

    -Nathan
     
  4. Michael J. Spangler

    Michael J. Spangler Well-Known Member

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    sorry i tend to put too much though in to what i'm trying to type to the point of not typing what i'm thinking about, if that makes any sense

    edited
     
  5. winmagman

    winmagman Well-Known Member

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    Well now, Those numbers look a heck of a lot better. By most folks standards you're still going a little to far for shoulder bumping. You should try to set your sizer up so your sized cases come out in the 2.462 ballpark, any more than that and you're working your brass more than neccessary.

    Chris
     
  6. Michael J. Spangler

    Michael J. Spangler Well-Known Member

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    ok cool thats what i thought. like i said i don't have any type of reference on this stuff, so i was making sure this was normal.

    the first reload i had just neck sized but i figured i could set up the die for a .001" to .002" bump.

    are there any good ways to set a die and not have to re-set it each time i want to switch a die out? i know my RCBS dies have a set screw on the lock ring, but are there any better ways?

    thanks guys. i love this stuff
     
  7. woods

    woods Well-Known Member

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    Other than setting the lock nut, I don't know of any other way to save your die setting. I put witness marks on mine to make it easier to set
    [​IMG]

    Set your shoulder back .001" or as close as you can get to that.
     
  8. Gene

    Gene Well-Known Member

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    The absolute best way to measure whether you need to bump and how much, is to buy a Redding Precision Mic with dial indicator. With this in your press and properly set up, you can measure every .001" of bump, so that you do not bump the shoulder excessively, and create unwanted negative headspace. Its so easy that I regularly run my cases thru it before sizing, takes seconds.
     
  9. trueblue

    trueblue Well-Known Member

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    Another way to set your die is to take a case that chambers stiffly due to headspace, and resize it until it chambers easier. Start with your die set high, resize the brass, chamber it, if it is still stiff to chamber, screw your die down alittle and do it again. Slowly work your way down until the brass is easier to chamber. But go slow, so you don't bump the shoulder back to far. I don't bump over .002 if I can help it.
     
  10. Cover Dog

    Cover Dog Active Member

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  11. Hired Gun

    Hired Gun Well-Known Member

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    Bump the shoulder?.......... Uhhh...... hmmmmmm. Measurement?? I just keep my bolts lugs lubed up and do that when I close the bolt. I try to neck size only with the old Lee Collet dies. That's a precision as this kid gets. I do bump them when I loose neck tension then I anneal and am good to go for another 5 times. I have to set up the die each time and then just only bump enough to get the bolt handle to drop with minimal resistance. No measures required. I do it by feel.

    The less you work on your brass the longer it will last. I have 7 mag and 300 Wby brass that have gone 30 times. The 257Wby is hard on primer pockets when I get greedy. The 22-250 brass is almost 20 years old now and it gets reloaded 2 to 5 times a year.

    Did I mention I like Lee Collet dies?
     
  12. Michael J. Spangler

    Michael J. Spangler Well-Known Member

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    good article thanks man

    yeah next order from midway is going to have a lee collet die on it.

    along with a bunch of other stuff
     
  13. Hired Gun

    Hired Gun Well-Known Member

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    300 RUM Collets are a custom shop item. You have to call Lee direct to get them made. This was last I looked. I haven't looked in over a year. Matbe they are a regular item now. They should be.