Headspace question

Discussion in 'Gunsmithing' started by relabbe, Apr 30, 2008.

  1. relabbe

    relabbe Active Member

    Messages:
    27
    Joined:
    Feb 3, 2006
    I just put a new 300 win mag barrel on my 700 remington long action. I have a gunsmith book that states that the go gauge will fit if there is .220 inches. I used a new bullet and a shim on it back to measure my head space and I have about .218 inch of headspace. I cycled the rest of the my bullets in my gun and they all cycle nicely. Do I still need that .002 inch missing? If I need them I guess I should be lapping the lugs on my bolt.

    What do you think? any advice...

    Thanks,
     
  2. J E Custom

    J E Custom Well-Known Member

    Messages:
    7,273
    Joined:
    Jul 29, 2004
    My recomendation would be to buy a GO headspace gauge for
    that round and use the shims on the back of the go gauge to
    find the exact head space.

    They are very cheep (Normaly $30 to $40 dollars.Brownells
    sells Manson or Clymer.Mansons are a little cheeper and are just
    as good.

    I like .000 to.001'' but .002 to .003 will work.

    Factory Loaded ammo is sized on the small side to work in all weapons
    and if you use factory ammo to head space it will be smaller than SAAMI
    spec.

    And if you are .001 or .002'' less than you want then lapping the bolt is a good
    way to increase headspace.

    Better safe than sorry
    J E CUSTOM
     
    Last edited: May 10, 2008

  3. specweldtom

    specweldtom Well-Known Member

    Messages:
    1,064
    Joined:
    Jun 7, 2004
    I have had a couple of rifles that would not take a go gage, but would chamber new factory ammo and unfired cases. I left them that way without any problems. On the belted cases, you might need a little more room if you switch ammo or use reloads fired in another rifle. Headspacing on the belt makes them unforgiving if the chamber is even a tiny bit short. I like tight chambers for accuracy and case life, but you have to be sure that the ammo you use will chamber cleanly.

    I recommend getting your 'smith to try his go gage again, and if the bolt will close, then add shims until it won't. Then you will know exactly where you are. Presuming that the rifle is not a benchrest gun, if the bolt won't close on the go gage, I would touch the chamber with the reamer until the bolt will just barely close.

    This is just my opinion and preference.

    Good shooting, Tom
     
  4. relabbe

    relabbe Active Member

    Messages:
    27
    Joined:
    Feb 3, 2006
    Thanks J E Custom, I measured all my Factory Loaded bullets and the space between the ream and the head were all in between 0.215 to 0.218 inch. (winchester Supreme Nickel plated) which leaves a minimum headspace of.002 inch if your chamber is tight to the go gauge. The minimum headspace for the go gauge to fit is 0.220 inch and the no go gauge minimum headspace is 0.223. This means if you are using factory ammo and you are within the specification of the go gauge you can have up to .008 inch (0.223-0.215).

    If all the factory ammo were perfect (all the same length), what would be the optimum headspace?
     
  5. relabbe

    relabbe Active Member

    Messages:
    27
    Joined:
    Feb 3, 2006
    Thanks Specweldton, I guess I should try the go gauge.
     
  6. J E Custom

    J E Custom Well-Known Member

    Messages:
    7,273
    Joined:
    Jul 29, 2004
    Relabbe

    One more comment on head space.

    .008 is the field gauge max (If it will close on this gauge then it is
    rejected and considered not usable).

    If you want good brass life you need to be under ,003 head space.

    The reason for more .004'' is for better feeding in gas guns (M14,M16 etc)
    with no intent of reloading the brass.

    From an accurace standpoint "less is better". on the big weatherbys with lots
    of freebore .000" headspace works the best for me, But it requires careful
    sizing and reloading.

    J E CUSTOM
     
  7. Kevin Cram

    Kevin Cram <b>SPONSOR</b>

    Messages:
    1,156
    Joined:
    Mar 9, 2004
    You definately should use a go gauge. Remove the fire control and the ejector for a better feel too. If the bolt closes easily on the go gauge take a piece of clear scotch tape and attach it to the base of the go gauge. Trim the excess tape off with a razor blade. The tape is approximately .003" thick. The bolt should close nicely with just the go gauge and not at all with the scotch tape on. Don't rely on testing headspace using a piece of brass.
     
  8. relabbe

    relabbe Active Member

    Messages:
    27
    Joined:
    Feb 3, 2006
    As suggested I bought a go gauge and recieved it two days ago. First, I took the extractor and fire pin of the blolt, then I put the go gauge in the chamber and push the bolt on it. I couldn't close the bolt. Remember that I told you that I could put in some loaded factory ammunition in the chamber and close the bolt. Some were rubbing but they all fit in.

    When I made the order to Brownell I also ordered some lapping coumpound. I then decided to lap the locking lugs of my bolt. I lapped for 3 of 4 sequences and trying the go gauge between each and suddenly the go gauge went in. I then put a 2 thousand of an inch shim on the back of the go gauge and try it again. I could not close the bolt on it. I quess, I still have a tight chamber.

    Now I have to go to the range and fire that baby.

    Thanks for your support guys,
     
  9. J E Custom

    J E Custom Well-Known Member

    Messages:
    7,273
    Joined:
    Jul 29, 2004
    Perfect !!!!!!

    J E Custom
     
  10. NesikaChad

    NesikaChad Well-Known Member

    Messages:
    753
    Joined:
    Jan 28, 2007
    Call David Kiff, owner of Pacific Tool and Gauge.

    28 bucks for a Go gauge.

    My process when hanging a tube on an action.

    Strip the bolt of anything that has a spring or might alter a measurement. (fire control, extractor, ejector being the top three things to peel off the thing)

    Drop in your go gauge.

    Hopefully the bolt closes freely.

    Now, get yourself some .001" thick Starret shim stock and cut it into little tiny postage stamp shaped pieces that fit into the bolt face. A dab of grease will keep them from falling out.

    Start stacking shim stock until the bolt just "sticks" as you attempt to close.

    You now know how far past minimum SAMMI spec your HS is. (PTG GO gauges are minimum SAMMI spec unless ordered otherwise)

    The term I'd use when at Nesika was "GO +.001" or .002". . . (what ever it ended up at) for the documentation on all the guns my department built.

    This is useful long term in case an accident ever occurred (like a grenaded case for instance) You can repeat the test and know if the lugs were peened or if the chamber was bulged/stretched somehow.

    Good luck and keep em centered.


    EDIT: Sorry, jumped the gun. Sounds like you got it licked. Very cool.

    Hope she works!
     
  11. Max Heat

    Max Heat Well-Known Member

    Messages:
    385
    Joined:
    Feb 26, 2012

    If accuracy (among other reasons for eliminating ANY extra head space)) is top priority, wouldn't "GO + .000" be the most desirable result that could possibly be achieved, while still remaining within the sammi spec?

    I already know the answer to that would be "yes". If all of your guns came up to that exact number, I suppose that would put you in the position of being completely "golden".

    BEYOND SAAMI: Now this does stray a bit over-the-line, as far as the topic (as well as the spec) goes, but since the goal of the sammi spec is to assure universal interchangeability within a specific round, I am considering going out-of-spec on my next build.

    The scenario is that there are only 2 manufacturers of the brass, including factory loaded ammo. The firearm will be expected to chamber ONLY fresh brass (including factory loaded), and brass that has been fired out of itself. But whether or not it will chamber brass that has been fired (and thereby stretched) out of another gun, is a "don't really give a damn" situation, because it is a situation that is planned on being avoided. In that respect, you can consider it to be a "custom" build.

    With that in mind, my plan is to purchase at 50 rounds of each man's new brass, and set HS for +.000 on the longest case found, among the 100 purchased. That will likely put the HS at a "GO - .00x" number, meaning it would be outside of the sammi spec. Now I know that anyone's first thought (including my own) when they hear "out of spec", is "no good". But, the OOS would be on the "good" side. Among the many advantages I see, would be highest possible accuracy attainable, absolute minimal stretching of the brass, best possible gas seal, etc. And the ONLY disadvantage (that I can think of) would be that brass fired out of other guns MAY be too tight. But like already said, that is a non-issue for me.

    Now granted, if I was "smithing" a gun for somebody else, or the public in general, I would NOT stray outside of the SAMMI specs, for obvious liability reasons. Speaking of which, I better also add the disclaimer that "in no way, shape, or form, am I suggesting that anyone else try this (at home, or otherwise).

    Now that that's out of way, for the custom situation mentioned, can anyone (preferably experienced smiths), come up with any legitimate reason to avoid setting the HS via the procedure that I have outlined?
     
  12. Hired Gun

    Hired Gun Well-Known Member

    Messages:
    1,537
    Joined:
    Apr 21, 2003
    The thing you run into with sub min headspace is your sizing die may not be capable of bumping the shoulder unless you trim a bit off it.
     
  13. Max Heat

    Max Heat Well-Known Member

    Messages:
    385
    Joined:
    Feb 26, 2012
    That IS a point that I need to think about, considering that the sizing die WOULD be made to the "GO + .000" spec, right?

    Since I'd like to avoid altering the die, I see 2 options. One would be to ease up on the HS, allowing the brass to grow enough to completely fill out the die. But that would wipe out any advantage that would be sought from going to a "GO -minus" number, sending everything right back to square 1.

    Short of "shortening" the sizing die, the only saving grace that I can picture for maintaining the fresh brass's less-than-SAAMI length would be to utilize the camber of the rifle itself to perform the length (to datum line) sizing procedure on the cases, by means of fire-forming. But I'm not sure how reliable that would be, in practice.

    I'm going to have to decide on exactly how far I would be willing to lower the "bar". I'm not really sure exactly how short of the sammi minimum factory brass usually is, but I'm thinking -2 to -3 would be fine, and MAYBE -4 if the brass from the 2 mans (rem & noz) comes up very consistent at 4 under. I would not want to go any more than that though.

    But it now appears that I am coming full-circle, as I might as well just go +0, let the first shot stretch the brass out once, to the "standard" size, and leave it at that.

    How short of saami does fresh brass typically run?
     
  14. Hired Gun

    Hired Gun Well-Known Member

    Messages:
    1,537
    Joined:
    Apr 21, 2003
    I have measured factory ammo or brass is usually anywhere from .008" to .012" short in my zero headspece chambers. Just go to zero to .0005" over is where I like mine. Your first firing will blow it out to your chamber size and then go from there. Setting your sizing die firmly on the shell holder will get you very close. Even with an overspec long chamber you can get good brass life and great accuracy by neck sizing and only bumpng the should the amount needed to keep the bolt closing easy.


    Something to keep in mind, Headspace is only a very small component in rifle accuracy. Consistant neck tension, even powder charges, bullet seating depth and concentricity are far more important than headspace.