Newbie Question - "Go", "No-Go" check Question.

[rjbFL]

Thanks in advance.

I know there is a warranty, for "Just-In-Case" I purchased a Spare Parts Kit.

And since the Bolt and Carrier are subjected to repetitive force, I felt that purchasing a Complete Bolt Carrier so that if a part failed, I could just slide a new unit in place, then repair-replace the broken part on the original Bolt Carrier unit.

Questions:

1) Do I need to do a "Go", "No-Go" check?
2) After many rounds are fired, using the original, should I do a "Go", "No-Go" check again?
3) What is wearing, causing this problem?

 

[Rastoff]

Are you talking about a "head space" check gauge?

 

[rjbFL]

Yes, Head Space check gauge. It seems it needs to be checked?

 

[Rastoff]

I have calibrated these gauges for the air force, but never used one on my own guns. It wouldn't hurt to check the head space now and then, but I don't think it's s large concern as far as safety goes.

 

[WR Moore]

The parts that wear that may affect headspace are the locking lugs on the barrel extension and bolt. Most of the wear is simply wearing the parts to where the bearing surfaces match. This really isn't much of an issue for most of us and is entirely normal. You'll probably wear the rifling out before the bolt shows excessive headspace.

The big issue with the AR pattern is cracked bolt lugs. This requires bolt replacement and yes, the headspace should be checked when bolts are replaced. A lot of people don't, it's your rifle, you can destroy it any way you want. If you rebarrel, you should spring for a matching bolt. Carriers themselves are pretty much a lifetime item.

When you check headspace, the rifle and the gauges must be clean. Remove the extractor and ejector and clean the bolt face. [I'll admit to sometimes cheating and leaving the extractor in place due to the following sentence. I hook the gauges under the extractor to control them as they're entering the chamber.] Be gentle when placing the headspace gauge in the chamber DO NOT DROP THE GAUGE INTO THE CHAMBER! The gauge is hardened steel and damage to gauge or chamber may result. Also, don't drop the gauges on the floor.

If checking headspace IAW the tech manual, you use the entire carrier group. VERY gently move the carrier forward with slight pressure until the carrier stops. If the go gauge is in the chamber, the rear end of the carrier should be flush with the rear end of the upper receiver. If the no go gauge is in the chamber, the carrier should protrude from the upper receiver. DO NOT FORCE THE BOLT/CARRIER AGAINST THE GAUGES! You can check the headspace without the carrier, but you have to have a dummy carrier (PVC pipe). If doing it that way, the bolt all by itself should turn in the barrel extension with the go gauge, not turn completely with the no go gauge.

 

[rjbFL]

WR Moore thank you

Much information, Another question please:

I have seen a "Field Gauge" what is it used for and when?

 

[WR Moore]

The go/no-go gauges are used in barrel/bolt fitting and in checking lighty used rifles. The 'Field Gauge' is a gauge intended to check heavily used rifle headspace that may have reached the point where rebuild at a higher level maintenance facilty is required.......or at least that's the way they're supposed to be used.

As Pat Sweeny noted, field gauges are used by armorers in East Waziristan trying to sort out usable rifles from ones where rebuild is mandated for use by replacement troops in heavy combat. They'll work....for awhile. [You have to bear in mind that rifles and the troops that use them are considered expendables in military service. You don't expend them lightly, but if you must, you do.]

In short, if the rifle accepts a field gauge, it should be removed from use (and tagged out of service) and serviced by folks who know what they're about. Excessive headspace can be caused by excessive bolt/barrel extension wear, cracked bolt lugs, damaged chamber....I'm probably overlooking something. New barrel and bolt are the usual cures.

Please bear in mind that in semi-auto rifles, the bolt will force the cartridge against the forward part of the chamber by action spring pressure [within the tolerance limits of the barrel/barrel extension in the AR design]. When the cartridge fires, the cartridge and bolt-if the headspace is sloppy-gets a running start at the locking lugs in the barrel extension. This geatly increases the load on the lugs and accelerates cracking of the bolt lugs. It also does bad things to the fired cartridge case. Not a good thing, but deemed an "acceptable" condition if within the limits of the field gauge. If you aren't in East Waziristan, you can be pickier.

 

[rjbFL]

WR Moore thanks.