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Headspace

Slightly ClassicsSlightly Classics Member Posts: 25 ✭✭
edited October 2007 in Ask the Experts
Please explain headspace. Safety concerns. There are so many reasonably priced 8mm Mausers on the market right now I would like to buy one or more. The problem is the one's I've looked at bolts and recievers numbers don't match. I know one should have rifle checked by a gunsmith before purchasing but this is not possible. Is this something I could check with a gauge. Also are the gauges for one caliber or adjustible for more than one caliber. Thanks in advance.

Comments

  • Slightly ClassicsSlightly Classics Member Posts: 25 ✭✭
    edited November -1
    I have an Ar-15 that i would like to switch the barrel on. When i remove the other barrel and put the other on will i have to have any headspace gauges seeing how they are the same brand barrels. Thanks
  • Slightly ClassicsSlightly Classics Member Posts: 25 ✭✭
    edited November -1
    In a different topic, I was told to get headspace checked. What is headspace and timing? Thanks, Bill
  • Slightly ClassicsSlightly Classics Member Posts: 25 ✭✭
    edited November -1
    I HAVE AN ALL METAL DUMMY ROUND THAT APPEARS TO BE 30-06 CAL. THE HEADSTAMP READS IN PART "SHAKESPEARE" AND USA IN THE CENTER. CANT READ THE REST. ITS HARD SO DOES NOT SEEM SUITABLE AS A SNAP CAP. COULD IT BE A "GO" "NO GO" HEADSPACE GAGE? ANY INFO APPRECIATED.
  • Slightly ClassicsSlightly Classics Member Posts: 25 ✭✭
    edited November -1
    Can someone explain the simple definition of headspace and how it is measured? Are there different measurement points taken for different types of guns? My wife says it is the empty space between my ears.[:D] I understand the concept, but I would like to have it explained so I will have a better understanding. Thanks!
  • perry shooterperry shooter Member Posts: 17,105 ✭✭✭
    edited November -1
    Hello Head space is the difference between the length of the chamber vs the length of the cartridge. With out going in to details a straight walled case such as a 45ACP headspaces on the case mouth A rimless rifle case such as a 30-06 headspaces on the shoulder of the case and a rimmed case such as a 38 special in pistol or 30-30 in rifle headspaces on the rim. too little head space and you CAN'T close the action too much and the cartridge is too short and can when you fire it jump back and cause stresses on the gun . much more to it but that is the quick and dirty Timing can refer to many different things in many different types of fire-arms and I saw the reply to your first question I don't know what the replier was refering to .Edit Thanks tailgunner FINGER CHECK on first post on my part [:o)][:I][:0][:(][|)]
  • Tailgunner1954Tailgunner1954 Member Posts: 7,734 ✭✭
    edited November -1
    Addendum to PS's post (and he ment that with to little headspace you CAN'T close the action).
    A gunsmith uses 2 gauges to measure headspace, GO which is ground to the SAMMI minimum dimention and NO-GO which is ground to the SAMMI maximum for that cartridge. Normaly there is about a .007 difference between the 2 (there is also a FIELD gauge which is used by a military armorer to decide if the firearm should be scrapped). What he's checking is the distance between the bolt face and what stops the cartridge from moving further forward in the chamber.
    Timing would be how the parts move in relationship which each other, but not knowing what your working with I can't say if it would effect you.
  • JKJK Member Posts: 223 ✭✭✭
    edited November -1
    Another addendum for 2 fine posts. The go/nogo's are the answer for many, but they do not tell you just how much it is on/off in between these 2 gages. Cut out a small pc of brass shimstock (.001) and attach it to the gage with some SAE 90, just so it will hold. If 2/3 pcs have to be held to the base and the bolt closes nicely on the gage, you can readily tell it's .002/.003 out. The two extremeties of the go/no go are the best means that we have to fit almost all situations. The shimstock is perfection
  • nononsensenononsense Member Posts: 10,928 ✭✭✭✭
    edited November -1
    Slightly Classics,

    Sometimes a picture is worth the proverbial 1,000 words:

    Headspacerimless.jpg

    This is a very good article about headspace and contains a number of illustrations:

    http://www.cruffler.com/trivia-October99.html

    Best.
  • CapnMidnightCapnMidnight Member Posts: 8,038 ✭✭
    edited November -1
    Nononsense,
    Laying here on my loading bench, I still have a head space and timeing tool for the 50cal machinegun, leftover from 29 years ago on my senior trip to SE Asia. Seeing the "headspace & timeing" made me think of it. Sorry, totaly off the subject.
    W.D.
  • cce1302cce1302 Member Posts: 9,555 ✭✭✭
    edited November -1
    quote:Originally posted by CapnMidnight
    Nononsense,
    Laying here on my loading bench, I still have a head space and timeing tool for the 50cal machinegun, leftover from 29 years ago on my senior trip to SE Asia. Seeing the "headspace & timeing" made me think of it. Sorry, totaly off the subject.
    W.D.


    I've only ever come across the importance of timing on the M-2 and M-48 .50 Cal machine guns. They are fired from the open bolt position. When you hold the trigger down, the bolt moves forward to slam the round into the chamber. I don't remember all the nomenclature, but timing prevents the firing pin from hitting the primer too soon, before the round is fully in the chamber, or too late, causing the bolt to slam into the front of the receiver, wearing out the gun prematurely.
  • givettegivette Member Posts: 10,886
    edited November -1
    CCE: givette here. M2-open bolt firing? Are you sure of that? I distinctly remember having to pull the charging handle back twice in order to chamber a round. (With belt inserted through the feed-slot)

    If open bolt firing, wouldn't the bolt lock back, preventing me from doing this?

    ....perhaps I'm confusing it with the M1919 (light '30). Dunno. Joe
  • iwannausernameiwannausername Member Posts: 7,131
    edited November -1
    Timing can also refer to the movement & positioning of the individual cylinders in relation to both the bore and firing pin on a revolver. Much like an engine (42 year old German and aircooled for me please), you want everything lined up and in the proper position before ignition.
  • v35v35 Member Posts: 12,710 ✭✭✭
    edited November -1
    Simply put, headspace is fore and aft clearance of a cartridge of standard dimensions in a chamber. Too tight and the bolt wont close or a cylinder wont rotate. Too loose and a cartridge may rupture from lack of support or not fire because the firing pin mayn't reach it.
    Timing in a revolver involves indexing a chamber with the barrel.
    The cylinder locking bolt must drop out of its' cylinder notch as the hand starts to rotate the cylinder. The hand must complete the rotation of the cylinder to the point where the cylinder lock drops into the next notch. The hammer must fall after the cylinder is locked. If any of these events don't happen properly, timing is off.
    Timing on Browning machineguns involves regulating the feed and firing
    parts of the cycle. I recall bending trigger bars with a ball pein hammer.
    Timing on the M2 carbine may likewise involve bending the disconnector lever or removing some metal to have the hammer fall after the bolt has locked up.
    M2-50 BMGs have blown up due to excess headspace before a modification in about 1953. A modified barrel detent spring and a hole in the frame were added to prevent headspace from changing when guns were moved in the field. A big guy was often delegated to carry the 110# gun assembled. Prior to the mod, headspace could be inadvertantly changed during these movements.
  • sandwarriorsandwarrior Member Posts: 5,453 ✭✭✭
    edited November -1
    Slightly Classics,

    Sorry for the lack of definition on my earlier post. Headspace is as shown and told previously the distance between a point on the shoulder and the face of the bolt. Each given round has a range of acceptable headspace. If you don't understand me or anyone else helping you, just ask. Don't feel embarrassed about asking on that post. Tons of really good information here and sometimes you even have to ask what you need to ask for, when seeking information. Not many places on the internet I think where you have such a wealth of people with mental libraries on the subject of firearms such as this.

    My mind must have drifted back to my military days when headspace AND timing was a phrase often used to describe the way you are thinking in a given situation. Mine must've been off a bit so as not to give a proper definition.

    Timing in the case of a bolt action is nothing more than when the headspace is correct and the bolt lugs are rotated all the way home, the firing pin will be at max extension and the bolt handle will be all the way down.

    In the case of the Ma duece...which I barely used in my day....timing refers to the point at which all the parts do their necessary job without catching on or getting in the way of another part doing it's job, after the headspace is set. Headspace and timing tools are typical with machineguns that need to have barrels changed out frequently.
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