M&P 15 headspace
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JaPes
Member
http://youtu.be/IWTpPMYW-CA
If your barrel is marked 5.56 NATO, then it is reamed to 5.56 spec. A new 5.56 NATO rifle shouldn't close on a 5.56 no-go gauge. Reminder: in order to check headspace remove the extractor and ejector from the bolt.
If your barrel is marked 5.56 NATO, then it is reamed to 5.56 spec. A new 5.56 NATO rifle shouldn't close on a 5.56 no-go gauge. Reminder: in order to check headspace remove the extractor and ejector from the bolt.
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JaPes
Member
Since the 5.56 NATO round and specifications are standardized under STANAG 4172, the chamber specs are not dictated by individual manufacturer.
http://www.ammunitionstore.com/content/5.56×45mm NATO.pdf
As long as I am using a chamber gauge produced by a reputable manufacturer or sold by a reputable distributor, I will reasonably trust the gauge.
http://www.midwayusa.com/find?userSearchQuery=5.56+headspace++gauge
If you question the validity of the Colt field gauge (I'm assuming a go gauge), try the gauge in a couple other rifles that are known/verified to be correct. Then you'll know whether or not the gauge itself is.
Any 5.56 chambered rifle (new or used) should not close on a no-go gauge. Any new 5.56 chambered rifle or used rifle still in spec should close on a go gauge.
Is the colt field gauge a "go" or "no-go" gauge? When gauging the chamber, did you remove the extractor and ejector from the bolt to get a true reading? What is the estimated round count of the M&P rifle? What is the model? Is the barrel stamped 5.56 NATO?
I'm also curious as to why you're seeking out this information. Sometimes I encounter people looking to buy a used rifle and they just want to verify that the rifle is in reasonable working order. I know of some people who are trying to build a rifle and are trying to gauge the condition of a slightly used barrel they can get for less $$$. Some people want to gauge a Franken-AR someone else assembled.
http://www.ammunitionstore.com/content/5.56×45mm NATO.pdf
As long as I am using a chamber gauge produced by a reputable manufacturer or sold by a reputable distributor, I will reasonably trust the gauge.
http://www.midwayusa.com/find?userSearchQuery=5.56+headspace++gauge
If you question the validity of the Colt field gauge (I'm assuming a go gauge), try the gauge in a couple other rifles that are known/verified to be correct. Then you'll know whether or not the gauge itself is.
Any 5.56 chambered rifle (new or used) should not close on a no-go gauge. Any new 5.56 chambered rifle or used rifle still in spec should close on a go gauge.
Is the colt field gauge a "go" or "no-go" gauge? When gauging the chamber, did you remove the extractor and ejector from the bolt to get a true reading? What is the estimated round count of the M&P rifle? What is the model? Is the barrel stamped 5.56 NATO?
I'm also curious as to why you're seeking out this information. Sometimes I encounter people looking to buy a used rifle and they just want to verify that the rifle is in reasonable working order. I know of some people who are trying to build a rifle and are trying to gauge the condition of a slightly used barrel they can get for less $$$. Some people want to gauge a Franken-AR someone else assembled.
cyphertext
US Veteran
Hey JaPes, the Colt field gauge is a no go gauge, as the bolt should not close on it. Also, if it is a true USGI field gauge, you don't have to disassemble the bolt.
