Excessive Headspace!

Discussion in 'Gunsmithing' started by Johnny5, Dec 15, 2009.

  1. Johnny5

    Johnny5 Member

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    So here's the deal, I have excessive headspace on my .338 Lapua (Timeberwofl Action). I confirmed this with a no-go gauge and some .003 paper. The best I can figure it is somewhere between .005" and .010" over the no-go gauge tolerance. This explains alot of problems I have been having including:

    -Failure to extract un-fireformed brass. This was my first indicator but the gunsmith assured me the headspace was fine and opened up the extracotr claw instead.
    -Excessive force required to full length size brass.
    -Near case head seperation after firing full length sized brass.

    The accuracy has been erratic but I'm not sure if this is attributable to the headspace or not as most of the rounds I fired were necksized only.

    Anyhow for all the gunsmiths on the board could this have caused any damage to the action (It's been fired around 200 times)? I only want to know because I would like to know how far I should be going with the gunsmith on this one.

    Another questions is how much headspace should there be for optimum function and accuracy? The intent for the rifle is a long range hunter in conditions which don't require a "loose" chamber so accuracy is primary.

    Thanks,

    -John
     
    Last edited: Dec 15, 2009

  2. NesikaChad

    NesikaChad Well-Known Member

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    Everything needs to be checked, double checked, and then checked again.

    It's the only way to know.

    Chad
     
    Last edited: Dec 15, 2009

  3. Johnny5

    Johnny5 Member

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    I contacted PGW to ask whether or not that would damage the action or bolt and they assured me the action was plenty strong enough to take that with no damage which puts my mind at ease some. Still ticked that alot of good and very expensive brass was ruined and the chamber needs to be re-done but at least I'm not screwed on the action.

    Can anyone suggest what the optimum headspace should be. The Kiff gauges give a .005" tolerance between the go and no-go, is there some kind of sweet spot in there or anywhere in that range is good?

    -John
     
  4. NesikaChad

    NesikaChad Well-Known Member

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    Here's what I do:

    I don't own any NO GO gauges. Not one.

    I buy all my GO gauges from PTG.

    I have a spool of .001" shim stock made by Starret.

    Strip the bolt of anything that has a spring or plunger. Drop in your gauge and allow the bolt to go home. It should rotate into battery under the weight of gravity.

    Now start cutting little postage stamps of shim stock and sticking them to the bolt face with a dab of grease. Keep stacking until the bolt handle no longer wants to rotate.

    The way I refer to this dimension is "GO plus whatever the number of shims are."

    This can be a very valuable tool to a guy if he starts doing this from day one, especially with a "boomer" magnum.

    Say on day one of receiving your rifle you do this and you come up with "GO+.002" for a headspace dimension. Now a thousand rounds later you check and it's changed to "GO+.006". Obviously something has moved. It could be the lugs have peened back, something is wearing, whatever. You at least had a starting point that a GO/NO GO can't provide by themselves.

    Last, it allows a guy to set his dies up right at the bench. If you measure your chamber and then replicate this by running your die to the same point you should have a more accurate representation of your chamber's depth so that you don't push the shoulder back further than it needs to be. Just plop the gauge in the shell holder with the shims in place and screw the die to the gauge. Perhaps remove a shim or two so that things chamber easily.

    That's my way.

    Chad
     
  5. Rustystud

    Rustystud Well-Known Member

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    Dave Kiff is in the business of making custom tooling. He will make reamers and gauges to almost any specification.

    SAAMI spec Go and No Go gauges differ by .0035" not .006.

    We all know that we fire form to make wildcats. We also know that outside SAAMI specs things can get dangerous very quickly.

    I would highly recomend you have a reputable gunsmith check your gun.

    When shooting magnums at the top end of the presure grid there is no room for error.

    I agree that what Chad Dixon said about using shims works. However, if you are working in a shop that has liability insurance, they require the use of "steel gauges, both Go and No Go." It takes any guess work out of the equation.

    Nat Lambeth
     
  6. KDB

    KDB Well-Known Member

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    Nat and Chad...This is obviously a novice question, but you both are very keen dudes, so I am going to ask anyway.

    What is the optimal number for headspace? Is it as close to zero as possible, or is there a need for some minimum tolerance, eg .001-.002 and why? Is it caliber specific or standard across the board?

    Thanks in advance.

    KB
     
  7. J E Custom

    J E Custom Well-Known Member

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    The amount of head space will vary depending on the rifles use.

    I would recomend a max of .003 for factory rifles that only shoot factory ammo because it
    varies in size and if you don,t reload brass is not a problem.

    For the accuracy buff I will normally set head space less than .0015.

    And for the belted cases I like .0005 to minimize brass stretch at the first firing.

    As a general rule I would say that .001 to .003 is the best range for head space and then
    minimum sizing of reloads.

    The only thing I would recomend other than getting the head space issue resolved is to toss
    the brass that you fired in it because with excessive head space case head separations
    are common due to stretching the web area of the brass.

    Hope this helps

    J E CUSTOM
     
  8. specweldtom

    specweldtom Well-Known Member

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    Johnny S and KDB, unless it was for a dangerous game rifle, I would set headspace as tight as it would go and still chamber unfired brass. I believe it helps with accuracy, brass life and safety. I have had 2 rifles that would not close on a go gage, but would chamber new brass. I left them that way. They never gave any problem of any kind and were very easy to full length resize. The rationale for me is that the Saami spec go gage is long enough to allow any brand of Saami spec ammo to chamber in a gun, so there is already quite a bit of room in a chamber that can just barely take a go gage.

    On go and no-go gage lengths, I've never checked the difference in the belted magnum go and no-go gages, (I don't have no-go's) so I don't know what the differential is, but from memory, the headspace gages for shoulder headspaced cartridges that I do have both gages for allow about .006" differential.

    I like to use go gages and shims like Chad, and I prefer go gages of the same brand as the reamer. I haven't bought a no-go gage in a long time, but I still use them in Garands and M1-A's.
    If either one of them will close on a no-go, It has to be rebarreled. I've swapped out a lot of bolts, and never had one that would make up more than .0015", and that's not enough to bring a gas gun far enough back from maximum headspace. I have the G.I. field test bolt and gage for M1-A's, but never used them.

    Sorry about getting long-winded, but headspace is critical, and there is no excuse for getting it wrong. The reason for no-go gages is safety. Excessive headspace can be catastrophic. If you want to crowd a headspace gage, go for tight, not loose. Anything over no-go is unacceptable, and .005"-.010" over no-go is scary. Don't fire another round until it's set back and headspaced properly, whoever you have to get to do it.

    Good luck, Tom
     
  9. Johnny5

    Johnny5 Member

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    Thanks for all the responses. I spoke with the gunsmith that did the work and he requested I send it back to the shop so he can fix it and figure out how it managed to leave the shop with improper headspacing.

    They typically do very good work and I know they will honor their mistake so I am not going to push the issue. However it was a sobering reminder to trust your gut when something just doesn't seem right.

    I am going to have him set the headspace for 1-2 thousandths max.

    Thanks again,

    -John
     
  10. NesikaChad

    NesikaChad Well-Known Member

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    Pretty much what JE said. It is largely application specific. a rifle that will only be fed carefully hand tailored ammunition can be chambered on the conservative side because of this. A working field gun that will be fed what ever the sporting goods store has on the shelf that weekend will typically get loosened up some. Same thing with breech clearances. Rifles that see a sterile environment can run tighter. Do that with a sniper rifle and it's possible the owner may go home in a bag because his rifle locked up tight on him.
     
  11. KDB

    KDB Well-Known Member

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    Thanks for the reply. So, if headspace specs is application specific, what is head clearance and how does get determined?

    Thanks again.

    KB
     
  12. Rustystud

    Rustystud Well-Known Member

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    Chad has responded very appropriately. Yes, he is a smart dude.

    I have great respect for him. He and I tend to be be a little more on the independent thinker side. Sometimes we catch hell for that.

    Have a great holiday and may your rifle return to shoot great.

    Nat Lambeth
     
  13. NesikaChad

    NesikaChad Well-Known Member

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    While I certainly appreciate Mr. Lampert's kind remarks I'm afraid now I'm going to sound anything but smart. I don't know what head clearance means. I've never heard that one.

    If your referring to bolt/breech face then again I base that on the application. A "bench queen" runs tighter (because most customers will have a brain seizure/fit if it's not done that way) where's a working gun gets loosened up so that it'll function in a broader range of conditions.


    I'm going to go out on a bit of limb here to try and put some of this into perspective. Let me preface this by plainly stating that IF YOU DON'T KNOW/UNDERSTAND WHAT YOUR DOING STOP IMMEDIATELY AND SEEK THE COUNSEL/GUIDANCE OF AN EXPERT.

    There, hopefully that'll thwart the "sea lawyers" out there.

    The truth is if a guy was to build a rifle in his basement and screw up the headspace by .005, .010, .015" etc, it's still not quite as big a deal as it's often made out to be. SO LONG as a competent handloader, who understands how to compensate for it, does the handloading work.

    You seat that bullet a mile long so that you know beyond the shadow of a doubt that the case head is firmly seated against the bolt face and you fire form the brass. This is nothing more than wildcatting 101. That's all your really doing. If our hypothetical homegrown gunplumber puts the kabosh on a 308 Winchester by gauging it with a NO/GO during chambering by mistake it is not a cardinal sin for him to use that gun. All he's done is create a ".308 Brainfart Improved" and now he has a little extra work to do when loading that first batch of ammunition.

    If the shoulder is allowed to blow out to the chamber shoulder nothing really gets upset or hurt because of it.

    HERE IS THE PROBLEM:

    If this rifle were built for or sold to another person who isn't as careful or who lacks the experience to know what is truly going on then the person who built the rifles is very foolish/reckless and they deserve everything the attorney(s) are going to unleash on him. The reason being is if this poor bastard were to start running factory loaded ammunition through this fuggered/hybrid chamber then it is quite possible/likely going to "sneeze" a cartridge case and send someone to the ER. Ignorance is not bliss when facing the laws of physics.

    Make sense?
     
    Last edited: Dec 17, 2009
  14. KDB

    KDB Well-Known Member

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    I think that the bolt/breach relationship is what I was trying for. I am interested becoming more knowledgeable about the finer details of gunsmithing, but am no machinist. I was reading an discussion on Benchrest Central, in the gunsmithing section, where there was what I would describe as a heated agruement over headspace vs head clearance in regards to a new measuring tool made by Larry Willis.

    To make a long story short, it got me thinking about the relationships between chamber, case and bolt and how those dimensions/specifications affect accuracy (if any) and case life. Further inspired by this thread, I thought that I would pose the question.

    I guess that I wanted to know if there was a magic number and why. But it seems that there is a +/- tolerance up to saami spec's, depending on application and environment. In terms of case life, more tolerance = more case streach resulting in bumping the shoulder back + degree of tolerance when FL sizing. So, if I am on track in simplistic terms, then do these measurements have any +/- effect on accuracy potential, real or theoritical?
     
    Last edited: Dec 17, 2009