Okay, I guess I'm just a moron...but I am trying to figure out this "headspace deal", and I've looked at the tutorial on this site, looked through TM/FMs but don't have all those fancy guages, etc. Has to be a simple way to do this! HELP
headspace confusion
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Okay, I saw the tutorial but what I am confused about it why would you adjust it 3-4 more times when the bolt closes and locks up flush? And, which direction do you ratchet it? I mean, do you want the bolt to close flush or don't you?
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3-4 click out is the military feild headspacing way I think. The 3-4 click deal is set with no bullet in the barrel. If everything is right when you put your bullet in you bolt should lock up and the shell should be snug in the chamber. With so many different manufactures of ammo you really should head space to the ammo. To add more head space you turn the barrel clockwise when you are standing behind the gun. You don't want to run anymore headspace than you need to. To much headspace and I will really go boom. Not enough headspacing and the bolts will not lock up or the gun will run slugish. I was using Federal brand military surplus and I was only at 2 clicks out. Please read this thread. It helped me out alot. http://1919a4.com/forums/showthread.php?t=818
Not enough headspacing and the bolts will not lock up or the gun will run slugish. I was using Federal brand military surplus and I was only at 2 clicks out. Please read this thread. It helped me out alot. http://1919a4.com/forums/showthread.php?t=818
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If you want to avoid blowing up your gun, just follow the "adjustment with parts inside the receiver" method listed below. It's very simple and fool-proof as long as you are using a GI barrel and quality ammo. DO NOT USE A CARTRIDGE OR DUMMY ROUND WITH THIS HEADSPACING METHOD. THE CHAMBER SHOULD BE EMPTY!
The official head-space method relies on the barrel and ammo being in spec (it will be w/ GI barrels). If your barrel is after-market and bad quality (chamber depth relation to breech face must be exact), or you're using really crappy out-of-spec ammo, only then should you vary from the below procedure. If you decide to use an alternate head-space method from what is itemized in the below field training manual, you better know what you're doing or you'll likely blow-up your gun.
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The official head-space method relies on the barrel and ammo being in spec (it will be w/ GI barrels). If your barrel is after-market and bad quality (chamber depth relation to breech face must be exact), or you're using really crappy out-of-spec ammo, only then should you vary from the below procedure. If you decide to use an alternate head-space method from what is itemized in the below field training manual, you better know what you're doing or you'll likely blow-up your gun.
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Read #3 in this. http://www.1919a4.com/forums/showthread.php?t=818
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Just to add a little more confusion to the confusion..... In order to understand what headspace is, it the distance from a theoretical line that is about ? half way up the shoulder to the base of the cartridge. The whole thing about headspace being different i.e.; 2 clicks out or 3 or 4 is that inspite of careful manufacturing, there are differences in barrels. When you screw the barrel in to the point that the bolt doesn't go into lock, the barrel is in contact with the bolt. So, in the gun itself the headspace is the distance from the theoretical line in the barrel to the bolt face. It's a nice theory but in fact there are broad variations in barrels. This can be checked by removing the barrel from the gun, cleaning the chamber out throughly, inserting a cartridge in the chamber and checking the distance from the base of the cartridge to the end of the barrel with a depth micrometer. Just a quick check of my 8mm and 30-06 barrel reveals that the 8mm cartridge protrudes out .115 past the end of the barrel and my 30-06 protrudes out by .123. Logic would tell you that the dimension from the face of the bolt to the area where the cartridge base actually rests remains constant since you don't change the bolt but the barrels become the unknown. I still haven't gotten a chance to go out and shoot the 8mm yet, but I suspect that becaue of the .008 difference, I will have to back it out 1 additional click from where it was from with the 30-06. I haven't checked my 7.62 barrel, but by calculating the thread pitch on barrel and the ammount of movement per rotation it can be easily calculated the number of clicks out for the correct headspace. Of course there will be manufacturing tolerances from the ammunition to deal with as well.
But the long and short of it is this. If it works well, don't mess with it.
But the long and short of it is this. If it works well, don't mess with it.
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Not to be contradictory, but headspace on a 1919 is defined as the distance between the face of the bolt and the rear of the barrel.
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loboslanding said:
True! But the rear of the barrel relationship to the chamber depth needs to be in-spec for the head-spacing to be correct when using the distance between the face of the bolt and the rear of the barrel to adjust head-space. If the chamber was reamed too shallow, too deep, or too tight because of an out of spec or commercial chamber reamer, the head-space will be incorrect if using the distance between the face of the bolt and the rear of the barrel as the means of setting head space.
Note: Out of spec chambers are typcially seen on after-market barrels of poor quality.
I know that you know all this Lobo. I am just clarifying it for the other posters.
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M14, to answer your question, headspacing is to allow for expansion when the gun heats up. That slop of 2 or 3 clicks will quickly get diminished after a few rounds. After lockup (point 0) you want to ratchet it out (clockwise looking at the rear of the barrel) the proper number of clicks to increase the headspace.
On the other subject, maybe I didn't properly communicate my intent or explain myself correctly...sorry...so I'll try again.
If a shooter has to go out more than 4 or 5 clicks on a cold gun then they need to find out why. If too much brass is sticking out the rear then the thickened base is out of the chamber and there is not enough support for the case walls when ignited and blowouts are eminent. Do not in any way, form or fashion compensate for a shallow chamber by increasing headspace...too much unsupported brass will be exposed; very bad ju ju.
Don't keep turning the headspace out if the barrel is that far out of spec. We have had numerous rear case separations and I suspect that this is one reason why. If we notice, most of the blowouts are with 8mm which almost all barrels are after-market commercially produced which probably don't have the same QC as GI barrels. I seldom hear where a separation has occured with a GI or Izzy barrel in 30-06 or 308.
Headspace is still defined as the distance from the bolt face to the rear of the barrel...if you have to use any other definition than this then toss the barrel or get it reamed properly. Headspace will always be correct using this definition...if it isn't then fix the barrel and not the headspace. Setting headspace with micrometers instead of counting maximum clicks can result in too much brass exposed and unsupprted. Measuring from the case head to the barrel face on a "good" barrel and then maintaining that same dimension on a barrel with a shallow chamber by running the headspace out is asking for big time trouble. This practice will result in brass in the a$$.
I know that nobody is actually intentionally saying to do this, but new guys don't need to even go down the path of picking up anything more than a screwdriver (or hs tool) to set headspace.
Not disagreeing...just clarifying that never under any circumstances should an out-of-spec barrel be fired. If the headspace can't be set using the published guidelines then don't fire the gun until the problem has been identified and corrected.
And to anticipate the next question of what is the proper cartridge protrusion...it don't matter. If you have to go out more than 4 or 5 clicks (especially when the gun is cold) then something is wrong. If you suspect a shallow chamber then ream it until you're down between 1 and 3 clicks out...or match a known "good" barrel chamber dimension.
On the other subject, maybe I didn't properly communicate my intent or explain myself correctly...sorry...so I'll try again.
If a shooter has to go out more than 4 or 5 clicks on a cold gun then they need to find out why. If too much brass is sticking out the rear then the thickened base is out of the chamber and there is not enough support for the case walls when ignited and blowouts are eminent. Do not in any way, form or fashion compensate for a shallow chamber by increasing headspace...too much unsupported brass will be exposed; very bad ju ju.
Don't keep turning the headspace out if the barrel is that far out of spec. We have had numerous rear case separations and I suspect that this is one reason why. If we notice, most of the blowouts are with 8mm which almost all barrels are after-market commercially produced which probably don't have the same QC as GI barrels. I seldom hear where a separation has occured with a GI or Izzy barrel in 30-06 or 308.
Headspace is still defined as the distance from the bolt face to the rear of the barrel...if you have to use any other definition than this then toss the barrel or get it reamed properly. Headspace will always be correct using this definition...if it isn't then fix the barrel and not the headspace. Setting headspace with micrometers instead of counting maximum clicks can result in too much brass exposed and unsupprted. Measuring from the case head to the barrel face on a "good" barrel and then maintaining that same dimension on a barrel with a shallow chamber by running the headspace out is asking for big time trouble. This practice will result in brass in the a$$.
I know that nobody is actually intentionally saying to do this, but new guys don't need to even go down the path of picking up anything more than a screwdriver (or hs tool) to set headspace.
Not disagreeing...just clarifying that never under any circumstances should an out-of-spec barrel be fired. If the headspace can't be set using the published guidelines then don't fire the gun until the problem has been identified and corrected.
And to anticipate the next question of what is the proper cartridge protrusion...it don't matter. If you have to go out more than 4 or 5 clicks (especially when the gun is cold) then something is wrong. If you suspect a shallow chamber then ream it until you're down between 1 and 3 clicks out...or match a known "good" barrel chamber dimension.
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Looking at all the posts since this AM, the statements are absolutely true. The headspace method using the datum line on the shoulder is defined by SAAMI as a standard. The micrometer measurement is an indicator used to make sure that the chamber isn't shallow, in which case there is a possibly dangerous condition since there would be more unsupported brass near the head. With the large number of barrel manufacturers out there there can be some wide variations and checking and double checking against known good barrels just means more safety.
"Don't keep turning the headspace out if the barrel is that far out of spec. We have had numerous rear case separations and I suspect that this is one reason why. Don't compensate for a shallow chamber by increasing headspace; bad ju ju."
Thoughts?
"Don't keep turning the headspace out if the barrel is that far out of spec. We have had numerous rear case separations and I suspect that this is one reason why. Don't compensate for a shallow chamber by increasing headspace; bad ju ju."
Thoughts?
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