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Thread: how to use headspace gauges?

  1. #31
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    Quote Originally Posted by Spooky130 View Post
    How exactly is a bolt "fitted" to a barrel?

    Spooky
    I dont know if this procedure is the right way to do it but we have done it more than a few times.

    remove barrel extension and remove .001" of metal from the step where the barrel extension rest and also from the where the bolt lug are to touch thereby moving the barrel extension forward by .001" yet maintaining the void for the bolt lugs to fit in.

    if you still dont get the right fit, repeat the procedure again.

    I have not yet made the 5.56 mm field guage cause I figured that if we will be fitting bolts this way then I'll just have to use the .223 field guage and get a better fit.

  2. #32
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    Apologies for resurrecting a 3 year old thread, but I figured better this than start a new one.

    Anyways, I recently purchased a Clymer's Field Headspace 5.56/.223Gauge from Bushmaster and was researching the proper use (thanks for the lead on that Iraqgunz). There appears to be come conflicting information, so I have two questions to try to clarify:

    1) Do you need to remove the ejector for proper headspace?
    2) What else needs to be removed from the bolt or BCG?

    I read through this thread and the following thread:

    https://www.m4carbine.net/showthread.php?t=87829

    I also read through the instructions:

    http://www.brownells.com/userdocs/le...HS%20Gauge.pdf

    I just want to be clear on the proper use as I got a bit confused on the proper use of the Clymer/civilian version of the Field Headspace Gauge.

    The directions indicate that you need to remove both the extractor and ejector. However, in the linked thread, it appears that the ejector may not need to be removed, assuming that it is working properly and the spring allows it to retract in it's normal operation. It is my understanding that removal of the ejector is also somewhat of a PITA, so if it's not necessary, that's good.

    In this thread, Grant mentions to "not re-install the firing pin or cam pin" and that the extractor stays in, but the spring and insert is removed. However, Iraggunz indicates that the TM instructions are to put the bolt in complete. I understand that the TM instructions are for the USGI field gauge without the case rim.

    Regarding the installation of the cam pin back into the BCG/bolt, is that irrelevant since the bolt would bottom out in the bcg when all the way forward? Forgive my ignorance on the positioning of the bolt in the BCG when the bolt is in battery. I just assumed that the cam pin slot provided the stop for the bolt.

    I bought the field headspace gauge as I will be swapping out a complete BCG on a couple of my guns (semi-auto to full-auto, and different brand) and also just to have to be able to occasionally check headspace (just to be sure).

    Thanks!

    Quote Originally Posted by C4IGrant View Post
    Barrel can stay in the receiver. Generally on Go/No Go gauges, you just need to remove the Extractor spring and insert and then put the bolt back into the bolt carrier (do not re-install the firing pin or cam pin).
    Slide the BCG back into the receiver. The end of the bolt carrier should poke out the back of the receiver slightly. If it sits flush with the receiver, then you have a problem.

    C4
    Quote Originally Posted by Iraqgunz View Post
    I'll run it down the way it is in the TM and how it is done in the military.

    Insert charging handle, bolt assy. (that means complete), and bolt carrier into upper receiver.

    Insert headspace gage into chamber area.

    Press the rear of the bolt and carrier assy. and charging handle forward using light finger pressure into the chamber area.

    Bolt should not rotate into the locked position and the bolt carrier must protrude from the rear of the upper receiver assy. for proper headspace.

  3. #33
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    The cam pin and firing pin must be installed or the bolt will not turn to lock in the barrel extension. With the civilian version the extractor and ejector should be removed but it can be done by just removing the extractor. The ejector will compress and add more resistance but it will still work.
    Certified Glock Armorer

  4. #34
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    Quote Originally Posted by 5pins View Post
    The cam pin and firing pin must be installed or the bolt will not turn to lock in the barrel extension. With the civilian version the extractor and ejector should be removed but it can be done by just removing the extractor. The ejector will compress and add more resistance but it will still work.
    Ok. Thanks!

    When you use the headspace gauges with the case rim, do you remove the extractor completely? Or do you only remove the extractor spring and that little post?

  5. #35
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    You simply remove the extractor pin and extractor and then insert the gage into the chamber and push the bolt forward.

    Quote Originally Posted by drck1000 View Post
    Ok. Thanks!

    When you use the headspace gauges with the case rim, do you remove the extractor completely? Or do you only remove the extractor spring and that little post?



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  6. #36
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    Very good! Thanks IG!

    Quote Originally Posted by Iraqgunz View Post
    You simply remove the extractor pin and extractor and then insert the gage into the chamber and push the bolt forward.

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