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Posted: 5/24/2002 2:37:35 PM EST
UPS delivered some gun toys ystdy., upper receiver vise block, barrel wrench & "No Go" headspace gage so.., today i built up an upper, got'er all lined up, barrel nut torqued, bolt carrier, key, gas tube line up perfectly, looks great !!

drop in "No Go" gage..., push gently on the rear of the b.c. & bolt locks up wythout too much force, so i remove gage & try a live round, bolt locks up wyth about same force, out comes the push-pull trigger gage, takes 5 lbs. 3 oz. pressure to lock bolt on live round, headspace gage requires 5 lbs. 6 oz to lock up....

do i panic or what ?

the headspace instructions say this:"...if a rifle closes on a "NO GO" gage, it MAY have excessive headspace.If a rifle closes on a "NO GO" gage, it maystill be within the SAAMI Rifle Chamber tolerance. Next it should be checked with a field gage.......

so lacking a field gage i decided to check the "No Go" gage in my other rifles chambers, i have 6 AR-15s, much to my surprize the "No Go" gage was locked up on by all the rifles except my unfired Colt & my ALMOST new Bushy, the new upper & the uppers on the four rifles, i am positively convinced that non of them wud lock up on the field gage, due to the ft.lb. force required to lock up on the "No Go" & a live round.......

i belive that if any one invests in any chamber gages they make it a "Field" gage, if a "No Go" gage is "OK" then why have one ?????

Link Posted: 5/24/2002 2:54:26 PM EST
Since your bolt closes on the NOGO you will never know how much out of spec you are until you try the Field Guage. If I were you I"d find somebody with one a check it out, then you will know for sure.
Link Posted: 5/24/2002 4:40:20 PM EST
CACTUS JACK - strip the bolt of the extractor and ejector on the bolt you want to headspace. Then insert the 'NO GO' gauge, with a piece of masking/drafting tape the diameter of the end of the gauge, in the chamber of the barrel you want to check. Then again try to close the bolt/bolt carrier group as you did before. The masking tape is .0035 to .0040 thick and this will approximate the dimensional length of the 'FIELD' gauge. If the bolt/bc group closes on this you have a problem. If not you are OK. The 223 headspace range limits are 0.003 the 5.56 headspace limits are 0.006. E-mail if any questions. JarheadGunner.
Link Posted: 5/24/2002 6:10:29 PM EST
I understand the Headspace GO / NO-GO / FIELD gauges measure the chamber space and that each one is a bit longer than the previous by about .004"

My question is: What is the repair if the bolt closes on the FIELD gauge? New Barrel? New bolt assembly? What?
Link Posted: 5/24/2002 7:09:18 PM EST
good idea but i thynk i'll try gunners trick, i am not too worried about it, but it will not be fired till i am satisfied it is safe.....

jarhead gunner,
great idea, i was doing a search & found the dimensions, then got some shim stock, but any adhesive i put on wud change the parameters.., your trick is so much easier thanx

GREAT question !!
i belive i'd try a different b.c. assy. first.., BUT !! & isn't there always one , what did the brass look lyke at last fireing ? was it bulged at the base ? if so how much ? maybe a better first question is has this rifle ever been fired ? is it a make up ?

or........., is this a hypothetical Q. ??
Link Posted: 5/24/2002 7:11:28 PM EST
WRECK TECH - The 223 'GO' gauge measures 1.4636, the 'NO GO' gauge measures 1.4666, the 'FIELD' measures 1.4736. The difference GO-NO GO is 0.003, the difference NO GO - FIELD is 0.007. The 223 chamber specifications are much 'tighter' than 5.56. If the bolt/bolt carrier closes on a 'FIELD' gauge you definitely need a new barrel. You can try substituting bolts, but, you probably will not gain much, because throat erosion occurs in the area forward of the chamber and this erosion causes the headspace to become excessive. If the barrel is not chrome lined you may be able to set the barrel back and extend the life of the barrel. If the barrel is chrome lined you may be able to set it back if you can find and/or afford to buy a 'carbide' chamber reamer. These are quite expensive and the new barrel may be cheaper. JarheadGunner.
Link Posted: 5/24/2002 9:27:22 PM EST

or........., is this a hypothetical Q. ??

Yes, Very hypothetical.... I understand and have learned much about my rifle reading and killing more than a few trees based on info in this site, but headspace is something I've yet to get a good handle on. I had always thought it was something under my hat and between my ears....  
Link Posted: 5/25/2002 4:05:25 AM EST

i too have been plagued wyth that mysterious "headspace" bugaboo for many years, in fact since i was about 16, i first heard about it from an uncle who was talking guns, i have always wondered why the .223 Rem. was NOT belted.......
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