AR Sponsor
Posted: 12/19/2013 8:09:35 AM EDT
| Working on my first build and was just able to get and order in for Daniel defense barrel to go with my dd bcg. I was wonder what you guys recommend for checking headspace go/no go set or colt field gauge or don't worry about it since it's a DD barrel and DD bcg. |
|
Quoted:
Working on my first build and was just able to get and order in for Daniel defense barrel to go with my dd bcg. I was wonder what you guys recommend for checking headspace go/no go set or colt field gauge or don't worry about it since it's a DD barrel and DD bcg. I'd get a go/no go if you actually choose to check. If you were building a bolt gun, then it would be a must. But since an AR's bolt locks up in the barrel extension and not in the receiver there is very little you can actually do to fix headspacing if it is off. You can either find a different bolt (not whole BCG) that head spaces right, or you would have to machine the barrel extension/barrel. This is also a good thing because assuming that your bolt and barrel are built to spec they should headspace good enough. Ordering a barrel/gun from a custom builder they'd head space the barrel to your specific bolt though. |
|
Quoted:
Working on my first build and was just able to get and order in for Daniel defense barrel to go with my dd bcg. I was wonder what you guys recommend for checking headspace go/no go set or colt field gauge or don't worry about it since it's a DD barrel and DD bcg. In the last year I've had two barrels fail on headspacing, I consider checking it MANDITORY! |
|
My opinion: Don't worry about it.
If you MUST check your own headspace, first, read up on the requirements and recommendations and process. Use this link: http://lmgtfy.com/?q=site%3Aar15.com+headspace Then - purchase a quality GO gauge if you are concerned about pressure issues potentially caused by short headspace. |
| Headspace can also change over time if you are running hot, high pressure loads. Just checking a new barrel and BCG match up is not enough. Get a set of Go / No Go gauges and check from time to time. Excess headspace is dangerous, too. It stretches cases and produces ruptures. Insufficient headspace can produce a discharge with the bolt not locked into battery. That is very dangerous. Both conditions, iv extreme, can have catastrophic consequences to weapon and to the shooter. |
|
I have worked giving military weapons Technical Inspections (TI) and gauging. We were only issued NO GO headspace gauge. This is only to save money. We would never know if we changed out a bad barrel with one that had to little headspace that is was dangerous. too little headspace could "crimp" the bullet in place while firing and raise the chamber pressure to extreme pressure levels (but is saved money). We solely depended on the industry to supply properly made barrels that were made properly.
You can either have the same faith that we did (and saved $23.00) or buy a GO and NO GO gauge set and know. Oh yea... never found one that was wrong. But that was only for about 2 or 300 barrels. |
|
Quoted:
Headspace can also change over time if you are running hot, high pressure loads. Just checking a new barrel and BCG match up is not enough. Get a set of Go / No Go gauges and check from time to time. Excess headspace is dangerous, too. It stretches cases and produces ruptures. Bad, bad info. Headspace changes from wear. The pressure of the loads you shoot has VERY little impact. A given pressure is either in spec for the chamber or it isn't. Headspace changes from metal being removed over time by friction and abrasion, not hot loads. The wear occurs at the back of the bolt, and the inside of the barrel extension, primarily. GO/NOGO gauges would not even be worth a damn for measuring long headspace due to wear. Closing on a GO gauge simply tells you that the chamber is not short. Failure to close on a GO gauge (when properly used) tells you that the chamber is short headspace. Failure to close on a NOGO gauge tells you that the chamber is not longer than original factory spec. Closing on a NOGO doesn't tell you much.... other than the chamber is longer than the NOGO specification. Some in-spec NATO chambers will close on a civilian (SAAMI) NOGO, which is 1.4670", while a NATO NOGO is 1.4706". So closing on a commonly available NOGO is not necessarily a big deal. The proper gauge to inspect for wear, in which a chamber is deemed no longer serviceable, is the Colt Field II gauge, which is 1.4736" Long headspace in an AR15 from wear is never going to be as long as the factory headspace in the M249 SAW, which shoots the same ammo. That's a bogus argument. In general, long headspace can lead to case head separations, but they are common and I would not classify them as "dangerous". They certainly don't risk blowing up the gun. They simply vent the gasses out the mag. A minimal headspace of the M249 SAW is 1.4947". That is .0211" longer than what will fail a FIELD II gauge in an AR. Does that make the SAW unsafe to fire from the factory? (Hint.... NO) |
|
Quoted:
I have worked giving military weapons Technical Inspections (TI) and gauging. We were only issued NO GO headspace gauge. This is only to save money. We would never know if we changed out a bad barrel with one that had to little headspace that is was dangerous. too little headspace could "crimp" the bullet in place while firing and raise the chamber pressure to extreme pressure levels (but is saved money). We solely depended on the industry to supply properly made barrels that were made properly. You can either have the same faith that we did (and saved $23.00) or buy a GO and NO GO gauge set and know. Oh yea... never found one that was wrong. But that was only for about 2 or 300 barrels. The bold red is false. Too little headspace does NOT have any effect on the bullet. Headspace has NOTHING to do with that dimension. Headspace is simply a measurement from the bolt face to the datum line. http://ar15barrels.com/data/headspace.pdf Short headspace simply means the case either will NOT chamber because it will not physically fit, or there is no space for expansion of the brass case by design, therefore increasing pressure by reduction of volume, and increasing likelihood of hard extraction. I agree, using a NOGO alone is not very useful.... even moreso if that was a civilian SAAMI NOGO used on AR15 chambers which are primarily NATO or Wylde. |
|
I'm more talking about pre-fired brass and my own reloading experience. Guys here do reload.
I had one bolt action 700 Remington that I used almost exclusively for pressure development of hot handloads. Over time (years), it did start rupturing cases, eventually new cases. With loads that were previously "fine." Agreed, I was purposefully developing maximum loads, increasing charges until I saw evidence of excessive pressure such as out of spec case head expansion, an internal "ring" close to the case head, and or brass flow on the case heads, swiping case headstamp marks, or leaving ejector or extractor marks on the case head. I was young and fool-hardy. Some of the ruptures and gas releases, even though that is a very strong action with a "ring of steel" completely around the case head, were mild, but one was pretty dramatic It took that one to get my attention. To this day I wonder if I made a mistake with the powder scale. It doesn't take much when you are working with maximum loads. Upon inspecting the bolt after realizing that it failed the "no go" test and even a "field" gauge test, I could tell that the bolt face, itself, had become worn and pitted (little pit marks all over the face), perhaps from the heat of the ruptures, maybe the slamming back and forth during ignition (although the case is brass and thus softer). I don't know. As stated, I was young and stupid, trying to soup up a .280 Remington to 7mm Rem Mag velocities. I learned a hard lesson without getting injured. I had to replace the bolt. Everything else was fine. I have not seen that personally in an AR15, although I know of instances of case ruptures that have forcefully ejected and destroyed magazines. |
|
Quoted:
I was wonder what you guys recommend for checking headspace For a new barrel as per MIL-DTL-70599C DETAIL SPECIFICATION CARBINE, 5.56 Millimeter – M4. These measurements for minimum and maximum headspace are the same for all the M16 variants, and also for the M4A1. Which you will see that headspace is also a determining factor when it comes to a barrel's endurance of firing 50 cycles (6,000 rounds). Page 13 3.6.3.2 Headspace. —After the high pressure resistance test, each weapon shall be gagged to meet headspace requirement after proof firing. 3.6.3.2.1 Minimum headspace. —After the high pressure resistance test, the headspace shall not be less than 1.4646 inches when measured to the 0.330 inches datum diameter on the first shoulder of the chamber. 3.6.3.2.2 Maximum headspace. —After the high pressure resistance test, the headspace shall not be greater than 1.4706 inches when measured to the 0.330 inches datum diameter on the first shoulder of the chamber. Page 18 3.6.7.6 Endurance headspace measurement. —Headspace for weapons being fired with 30 round magazines shall be measured and recorded at the beginning of the test and at the completion of the 50th cycle. After the 50th cycle, the headspace shall not be more than .0028 inch greater than the initial measurement and shall not exceed .0024 inch over maximum (1.4706 inches when measured to the 0.330 inches datum diameter on the first shoulder of the chamber). Page 45 30 rounds —Burst- one complete trigger pull (3 round burst) every 5 to 8 seconds. 30 rounds —Burst - one complete trigger pull (3 round burst) every 2 to 5 seconds. 30 rounds —Semi-Automatic - rate of 10 to 30 rounds per minute. 30 rounds —Semi-Automatic - rate of 10 to 30 rounds per minute. Total : 120 rounds per cycle |
|
sswfnhtu520,
If you are still wondering how to apply this information? Obtain a Go Gauge measuring 1.4646, and a No-Go Gauge measuring 1.4706. When checking headspace, the bolt will close on a Go Gauge to pass this gauge for minimum headspace, and the bolt shall not close on the No-Go Gauge in order to pass this gauge for maximum headspace (for a new barrel). Once you have the necessary gauges in hand, make sure the gauges actually measure what is listed on each one by using a caliper to measure each gauge from its side that rests against the breech face to its .330 datum line. *note —now the maximum allowable headspace for a .223 & 5.56 barrel is checked with the Colt II Field gauge measurement of 1.4736. |
|
Quoted:
In the last year I've had two barrels fail on headspacing, I consider checking it MANDITORY! Quoted:
Quoted:
Working on my first build and was just able to get and order in for Daniel defense barrel to go with my dd bcg. I was wonder what you guys recommend for checking headspace go/no go set or colt field gauge or don't worry about it since it's a DD barrel and DD bcg. In the last year I've had two barrels fail on headspacing, I consider checking it MANDITORY! As a gunsmith, I agree with this. If the headspace is excessive it becomes a safety and accuracy issue. While headspacing is not usually a problem on precision matched bolt and barrel extensions on AR rifles, the nature of all of the builds these days using mixed parts can present a problem. A set of Go, no go and/or field headspacing gauges can be a good investment or take your build to a gunsmith to have it checked. In your case you are matching parts form the same manufacturer but not necessarily the same source. DD outsources many of their parts. . |
|
Every serious AR shooter needs access to a Forester precision AR headspace set. It is an exellent tool, especially for precision shooters. Take a look: http://www.brownells.com/gunsmith-tools-supplies/measuring-tools/headspace-gauges/223-5-56mm-match-rifle-headspace-gauge-set-prod42236.aspx |
|
Quoted: I just used a colt field guage on my last build as advise from someone on here, for a recent new build and no it doesnt close on it, but i have not shot it yet either, should i be worried or just go try it out? |
|
Quoted:
I just used a colt field guage on my last build as advise from someone on here, for a recent new build and no it doesnt close on it, but i have not shot it yet either, should i be worried or just go try it out? GO and NO GO do not provide the indicators of an unsafe condition. Failing a GO gauge means a round will not chamber, meaning it will not fire if all else is mechanically in order. A live round can be used in place of a GO gauge, obviously following all safety protocols. NO GO is an interim measurement that gives you a glimpse at the longevity of the headspace, but provides no indication of safety on the other side. Failing NO GO might mean unsafe, but will require another gauge to establish this. A FIELD gauge is the safety gauge, it tells you when headspace is excessive and unsafe. It is called "Field" because, obviously, it's intended to be a summary gauge for use in the field. |
|
Quoted:
Spread that story around and maybe you will find a volunteer to test fire it for you. Quoted:
Quoted:
I just used a colt field guage on my last build as advise from someone on here, for a recent new build and no it doesnt close on it, but i have not shot it yet either, should i be worried or just go try it out? What is this suppose to mean??? |
|
Below is what I found on brownells website on Q&A
about colt field gauge they sell. I think this anwer is from brownells staff for what it's worth. A: Yes - the Field gauge is used to determine if the rifle is still serviceable and is safe to fire. Slightly longer than a No-Go gauge, the Field gauge is used to measure the absolute maximum allowable, safe chamber headspace. If the bolt closes on a No-Go gauge, the Field gauge is used for an additional check. If the bolt then closes on the Field gauge, the rifle is considered unsafe to shoot, and you’ll have to have the barrel set back and re-chambered. It depends on application. This is used to check if safe to fire, but the GO and NO GO is a better choice for most applications beyond checking a used rifle to determine if safe and able to be kept in service. |
|
Quoted:
What is this suppose to mean??? Quoted:
Quoted:
Quoted:
I just used a colt field guage on my last build as advise from someone on here, for a recent new build and no it doesnt close on it, but i have not shot it yet either, should i be worried or just go try it out? What is this suppose to mean??? Beats me. As pointed out, failing a GO gauge check (i.e. it doesn't close on the GO gauge) indicates headspace is too short. IF everything else is mechanically in order the round shouldn't fire. A .223 NO-GO gauge isn't of much use in a 5.56 chamber. Even if it fails the .223 NO-GO, it may still be perfectly safe to fire. The FIELD gauge is the one that reveals whether headspace is so excessive as to be unsafe to shoot. If it closes on a FIELD gauge, don't shoot it. Myself, I use the GO and FIELD gauges. Of the two, the FIELD is the more critical, but I use them both. |
|
Quoted:
A .223 NO-GO gauge isn't of much use in a 5.56 chamber. The chambers are IDENTICAL, the throats are different, to check the throat you need to use a gauge like the one manufactured by Michiguns |
|
New barrels should be checked with Go and No-go gages with the bolt that will be used with that barrel.
A 5.56mm barrel that fails the No-go gage may have a short service life before failing the max chamber gage. Since ammo is not usually made to max tolerance a barrel that fails the Go gage may fire ok until the day the user drops in in that mag with ammo that is at max or greater. Over the years I have seen several barrels fail the Go gage, but never the 5.56mm No-go gage. Lately I have seen a few barrels fail the SAAMI 223 REM No-go gage, but passed the 5.56mm No-go gage. As PursuitSS posted the gages are the same for 223 REM and 5.56mm for a given measurement. The difference lies in the headspace specs for the two cartridges. |
|
Quoted:
Working on my first build and was just able to get and order in for Daniel defense barrel to go with my dd bcg. I was wonder what you guys recommend for checking headspace go/no go set or colt field gauge or don't worry about it since it's a DD barrel and DD bcg. The gauges are like 30-50 dollars and you'd probably only use them once or twice, if that. My advice is to go to a gun smith and ask them to do a quick check on it. Just take your upper and bolt and go there. It'll be either free or way cheaper than the cost of the gauges and S&H costs. |
|
Quoted:
Every serious AR shooter needs access to a Forester precision AR headspace set. It is an exellent tool, especially for precision shooters. Take a look: http://www.brownells.com/gunsmith-tools-supplies/measuring-tools/headspace-gauges/223-5-56mm-match-rifle-headspace-gauge-set-prod42236.aspx The match set is kind of excessive for testing whether or not a bolt/barrel combination is safe. GO and NO GO gauges will identify if a chamber is too tight for a given bolt (fail if the bolt won't close on the GO gauge) or too long (fail of the bolt will close on the NO GO gauge). The set in the link gives you a much finer level of measurement of the headspace dimension (the distance from the datum circle in the chamber to the case head). This may be useful for people with a dozen bolts and a dozen barrels they want to switch around, but a "serious" AR shooter can be comfortably safe with just the Forster GO and NO GO gauges (Brownell's part numbers 319-223-464WB and 319-223-467WB respectively). |
AR Sponsor