adjusting head space

Discussion in 'Reloading' started by devildoc, Apr 13, 2006.

  1. devildoc

    devildoc Well-Known Member

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    How does one adjust headspace on standard RCBS dies (I know, I need to upgrade), I'm using the stony point headspace gauges and I just want to bump the shoulder back .002". Do I set it up so the die is no longer camming on the shell holder and keep backing it out till I get the desired bump?
     
  2. Bart B

    Bart B Well-Known Member

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    Yes.

    I've got six .308 Win. full-length RCBS dies. When any one die is locked in one of three presses, the clearance between the same shell holder to the bottom of each die for what's needed to set shoulders back .002-inch varies several thousandths of an inch.

    All dies and presses are not made to exact specs. Tolerances prevail. Your die and press may end up with the die just clearing the shell holder without a case in it. Or there may be a bit of contact. I've measured the "headspace" in those dies with a GO headspace gage for chambers to see how far the gage protruded out the bottom of the die; they all ain't the same.

    Plus, I don't think there's anything wrong with those RCBS dies.
     

  3. LWolken

    LWolken Well-Known Member

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    Esentially yes you adjust the depth of the die to get the desired shoulder bump. Its hard to believe that reloading books just say to set the die adjust for where it slightly bumps the case holder. This does vary greatly and until I began measuring I was bumping some back .010" while some dies were not even bumping at all! So yes the dies are very inconsistent. I even had to have a Redding sent back to have the bottom cut down so I could touch shoulder at all. The right way is to measure it then lock the ring on the die and bingo your set.

    Lance
     
  4. cva54

    cva54 Well-Known Member

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    bear with me here so head space will only fall in to the game when reloading not with factory ammo so there is nothing I can change on my rifle other than replacing the bolt and checking with one of them stop and go dies I think that is the right name
     
  5. boomtube

    boomtube Well-Known Member

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    "How does one adjust headspace on standard RCBS dies (I know, I need to upgrade), I'm using the stony point headspace gauges and I just want to bump the shoulder back .002". Do I set it up so the die is no longer camming on the shell holder and keep backing it out till I get the desired bump?"

    Okay, first you have no need to "up-grade" anything, your dies are fine.

    Most people FL size the "right way", as the die insructions say and that is by screwing the die down to firm contact with the shell holder. Many, if not most, are actually over sizing and creating excess headspace that way when none need exist. Over resizing is the major reason many "experts" suggest we only load our brass five times before tossing it. Sized correctly, my cases last three to five times that many loadings, sometimes more. And I mean fulll pressure rifle loads.

    To properly adjust the FL sizer you need to accurately know the head to shoulder length of your fired cases. Use the Stoney Point tool to find that. Then, I believe it's simplier to back the sizer off a bit and work down toward the target length.

    Put your sizer die in the press and adust it so it touches the raised shell holder. Then back the die out a quarter turn, that moving the die about 16 thousanths of an inch up. Size a case then measure it's head to shoulder length. It will likely be longer than it was before sizing. Adjust the die down about 1/16 of a turn, that being about 4.5 thousants, and test it again. Keep this up until you get the case shoulder where you want it, 2 thou below fired length is a good target. It won't be totally consistant because brass isn't that consistant an alloy so some cases will spring back at the shoulder a little more than others. Secure the die's lock ring to save the adustment.

    Normal head space tolerance is about 8-9 thou, total range. If you move the die any more than 1/16 turn per adjustment you can cover more than the full range tolerance range quite easily. Go slow here.

    A Wilson type case gage (a "go-no go" type gage, or "stop and go") has a chamber precisely cut into a solid cylinder of steel. The cylinder shows both ends of the case and has a small step cut at each end. The mouth end is a case length gage, we trim if the case is higher than the step. The other end is a headspace gage and the head should be between the two levels to make the case meet SAMMI specs.

    SAMMI specs don't mean at thing to a competent hand loader working with his own rifle. The actual headspace length means nothing if a case properly fits the chamber in which it's fired. By adjusting your sizer as described above, your cases WILL fit your chamber, period. I no longer use my Wilson SAAMI case gages for anything except those rare occasions I load for someone else.
     
  6. kraky2

    kraky2 Well-Known Member

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    Boomtubes instructions are good. I'll add a couple of other tips...having used the same tool for a few years. Knock out the primer before taking your measurements...alot of times the primer can back out about .001 to .002 and goof up the measurements.
    The second tip being that you will usually have to fire your virgin brass 2 times before they fully expand to the length of your chamber. Often one firing will leave them .001-.003 shy of full expansion.
     
  7. MagMan

    MagMan Well-Known Member

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    This is good advice.

    This is also good advise but I'm on my 3rd & 4th firing of 338 Edge brass and have yet to bump a shoulder. So unless you can feel that things are tight when you drop the bolt I wouldn't worry about bumping the shoulder back. Though it may grow a little when you FL size without bumping the shoulder. It doesn't hurt to double check.
     
  8. Gene

    Gene Well-Known Member

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    First, are you using a magnum case or standard bottle neck case? Headspace is different on magnum, they measure on the belt. Bottle necks measure from base to datum line (about half way up the shoulder). When you turn down the bolt, is there stiff resistance? If so, you probably need to bump. Try to bump a minimal amount, not more than .003". Deprime the case, put the empty in the chamber. First remove firing pin if you can. If you feel hard resistance, turn your F/L die down a quarter of a turn at a time, keep resizing and turning down a quarter, until the case chambers with just a very small resistance. That tells you the case shoulder is touching the chamber shoulder and is just right. Going further creates dangerous excess headspace, and other problems as well.
     
  9. cva54

    cva54 Well-Known Member

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    so there is a way to check it and how do I check it what about putting a little clay on a vergin round chamber it (dont shoot it) pull it out and mic. it see were I am at now clean it off (shoot it) and recheck the case and do the math would that give me my head space ( I biuld car motorcycle HD engines so I got all kinds mic inside out side mics. and things for getting things with in .001lightbulb
     
  10. boomtube

    boomtube Well-Known Member

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    "Try to bump a minimal amount, not more than .003". Deprime the case, put the empty in the chamber. First remove firing pin if you can. If you feel hard resistance, turn your F/L die down a quarter of a turn at a time, keep resizing and turning down a quarter, until the case chambers with just a very small resistance."

    Gene, your idea is correct but your suggested adjustments to attain that .003" bump are off. Dies have 14 threads per inch. A quarter turn changes it a tad under .018". The .003" change you accurately suggest would be lost some six times in a single adjustment, moving the die a one quarter turn can take a case from not quite enough to way too much shoulder set back, aka excess headspace.

    My suggestion of a 1/16th turn covers almost .0045" thou, so even that is way more than would be ideal to attain a shoulder set-back of 2-3 thou. But it's closer!

    I move my size die in even more tiny increments once I'm within maybe 5-8 thou from where I want to be.
    ---------------------------------------------------------

    "...so there is a way to check (headspace) and how do I check it..."

    CVA, the clay should get you close, but why care? There are no tools to do that because few care. All we really need to know is how to resize our cases to fit our rifle. Even precision riflesmiths don't much care about the absolute figure, they only care if the chamber headspace is within the normal +/- specs. They confirm it with a simple, two item set of "go/no go" gages.
     
    Last edited: Nov 2, 2008
  11. kraky2

    kraky2 Well-Known Member

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    "until the case chambers with just a very small resistance. That tells you the case shoulder is touching the chamber shoulder and is just right. Going further creates dangerous excess headspace, and other problems as well"

    Not sure I understand this idea either....dangerous if you don't have resistance to closing??? Maybe some others like resistance to chambering but....not me...not for my hunting loads.
     
  12. Gene

    Gene Well-Known Member

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    Boomtube, you are correct; I did not give much thought to that statement. And I don't turn em down a quarter turn myself. I turn the die down just a fraction, try and if not enough do it again. There is a need for someone to design a shoulder bump measurement tool. You can have your gunsmith make one; think I paid $60 for the last one in 30BR. Harrels includes them (some guys call them a "thingy") with every new F/L die they sell. But, I have trouble getting consistent readings with it. The idea is you put a small thimble over the case mouth so that it touches the datum line (center of shoulder) , then use your calipers to measure base to the top of thimble before and after bumping. But this is real tricky. I have used a 45 ACP deprimed case to do this, but it is not much better.
     
  13. woods

    woods Well-Known Member

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    It looks like cvs54 resurrected a 2 1/2 year old thread and started asking about checking headspace on factory ammo and then putting clay on the shoulder, chambering the round and mic'ing it?

    All the answers were right on and very helpful to a reloader, even a novice one, but IMO y'all are performing an exercise in futility.
     
  14. lever-hed

    lever-hed Well-Known Member

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    Headspace is probably THE MOST important dimension on a case and chamber. There is nothing futile about headspace measurements.. Maybe for someone who knows what they're doing on they're rifle then it is an 'understood' issue. To this person, it is futile, but never forget, if you inadvertantly over bump or over size the case body, and forget to check, then uh-oh. I will do a check on headspace with a vernier micrometer and will check before neck sizing, usually they're tight at around +.002 to.003" over ANSI/SAAMI, there is a range of about ten thousands of inch, but this check just lets me know where I am in the case lifespan, and if I do bump the shoulder, I have a reference point . .