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Headspace
Slightly Classics
Member Posts: 25 ✭✭
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
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.
Sometimes a picture is worth the proverbial 1,000 words:
This is a very good article about headspace and contains a number of illustrations:
http://www.cruffler.com/trivia-October99.html
Best.
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.
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.
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
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.
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.