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Posted: 2/1/2011 8:35:05 PM EDT
I have a used FN 5.56 barrel, used Colt bolt and some .223 GO NO-GO gauges.
The bolt fully closes on the GO gauge leaving 1/16" - 1/32" of the carrier sticking out the back of the upper. I assume this is tolerable.
The bolt rotates and slightly (1/16" possibly) engages the extension lugs with the NO-GO gauge. Is this something I should be worried about?

I checked the chamber of my other AR tonight (Factory Colt) and the GO gauge seems the same as above. With the NO-GO gauge, the bolt enters the extension and rotates slightly engaging a little less than what happened above. Slapping the side of the upper with my hand made the bolt disengage from the lugs. (This did not happen on the above barrel bolt combo)

I assume that the results of testing my factory Colt with the .223 gauges gives a good example of what I should see. My question is, does the used FN barrel seem to headspace correctly given the information I have provided?

Link Posted: 2/2/2011 3:14:35 AM EDT
[#1]
the bolt should close on a GO gauge. the bolt should not close on a NOGO gauge. sounds like you're good to go
Link Posted: 2/2/2011 3:21:53 AM EDT
[#2]
your using .223 gauges on a 5.56 chamber
http://www.ar15barrels.com/data/headspace.pdf

eta do pull the ejector if the gauge does not have the clearance cut.
Link Posted: 2/2/2011 4:47:04 AM EDT
[#3]
Quoted:
your using .223 gauges on a 5.56 chamber
http://www.ar15barrels.com/data/headspace.pdf


And?  The mil uses a slightly looser headspace spec for reliability.  It also leads to excessive brass stretch.  Really has nothing to do with .223 vs. 5.56.  His chamber is good as long as it doesn't close on a FIELD gauge.  NO GO gauges are for gunsmiths doing the initial chambering of a barrel.
Link Posted: 2/2/2011 5:45:21 AM EDT
[#4]
Where does one acquire this field guage?  I looked at Brownells and can only find go/NO go......
Link Posted: 2/2/2011 6:48:42 AM EDT
[#5]
Link Posted: 2/2/2011 8:21:59 AM EDT
[#6]
Its best to buy the 556 if your doing a 556 and usually you only need the Go and the NO Go I usually don't use the Field gauge but to answer the question if your bolt closes on a go and dosent close on a no-go your fine.....
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