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Posted: 7/7/2014 6:08:06 PM EDT
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Hello,
I just finished my first AR build. Having built with good quality components, I expected my only issue to be the learning curve of a first assembly. I purchased a set of 223 Forster go - no go headspace gages and expected a quick and easy test to verify my headspace is within spec. If I understood the process correctly, indicators of proper headspace are:
My BCG and barrel are new and from the same manufacturer. I made sure to dis-assemble my BCG down to the bare bolt and carrier group (i.e. minus cam, ejector spring, etc.). Having done this and checking headspace I found that I could close the bolt all the way with the no go gage. Is this truly an indicator of improper headspace and if so is there a particular component I should be suspicious of? Should I be suspicious of the gages themselves? If I check the gage, am I just looking at an overall length? All components and gages were purchased new in packaging. Thanks in advance  .
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Closing on a NO GO indicates that it MIGHT have excessive headspace. If it closes on a FIELD then it does have excessive headspace. And make sure you are using the correct gauges. .223 in a 5.56, while for all intent and purposes are the same when it comes to ammo CASE size, the headspace gauges can be different.
This is a letter I got from Clymer a while ago regarding HS gauge differences between .223 and 5.56. Other companies have their own rules but this was from Clymer: Sir,
We set both GO gauges at SAAMI minimum (1.4636”). We set our 223 FIELD gauge at SAAMI max. (1.4736”) (we don’t label a field gauge for 5.56 but use the 223 to be safe). No Go is were we have different grind lengths for 5.56 and 223. No Go 223 Rem = 1.4666” (match) No Go 5.56 Nato = 1.4696” We hear the mfr’s chamber their AR’s deeper than say a bolt action to get them to cycle better. Makes sense to me. Thank you for your interest and we look forward to hearing from you soon. Best regards, Todd Wilms Ph 248-853-5555 Fax 248-853-1530 1605 W. Hamlin Rd. Rochester Hills, MI 48309 www.clymertool.com [email protected] So you see, if you have a 5.56 barrel and using .223 NO GO gauge, it could be perfectly fine, and more than likely is, and still close on a .223 NO GO gauge. In your case, I'd say you are using the wrong NO GO gauge and everything is just fine. I've yet to find new component barrel and bolts to not headspace correctly. When they don't, 99 times out of a hundred it is user error which I strongly suspect in this situation. Don't feel bad, we've all been there when we first started out. |
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The last Forster 223 REM Field gage I bought was 1.4696” and the No-go was 1.4666”.
AFAIK the US mil-spec for 5.56mm No-go is 1.4706”. It would appear that Clymer is using 1.4696” for their NATO No-go gage. So basically you do not have a problem unless it fails the 223 REM 1.4696” or 1.4670” Field gage. No you do not measure the overall length of the gage. There is a chamber drawing with specs on the SAAMI website. The gage measures from the base to a datum line on the shoulder of the gage. |
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If I understood the process correctly, indicators of proper headspace are:
From the above I don't think you understand the proper use of a headspace gauge. It appears when you are saying "bolt" above you must be talking about the bolt CARRIER. The proper use of a head space gauge in an AR type rifle would involve a stripped bolt (no extractor or ejector), inserting the guage and attempting to insert and lock the bolt into the barrel extension. It should close on the go and not on the no go. Please do a little more reading on just what headspace is and how to check it. |
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Quoted:
Actually there is nothing wrong with using an assembled BCG sans ejector and extractor. Correct. What I meant to point out was that the protrusion of the BCG from the receiver means naught. In fact using it might make it easier to manipulate the bolt absent the barrel not being mounted. |
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Quoted:
If the bolt will not lock the bolt carrier sticks out of the upper. This is all covered in the TM which is available on this and other sites. That's what I was getting at. Without the cam pin the bolt won't rotate to lock, and if headspace is close to excessive, without the cam pin the bolt can sit deeper in the carrier and the carrier could possibly be flush with the receiver |
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Thanks again everyone for the help. I do have an assembly manual and was checking headspace the way I had read multiple places to do it. It's always nice to get other peoples input. It does make sense that having the cam pin inserted might be a good idea. I was checking with a stripped bolt. Obviously my pass/fail indicator description was inaccurate. I understand the difference between the bolt and bolt carrier. I'll be more careful with the accuracy of my words in the future and not throw them around interchangeably. For sure, I'll continue to read up on head space.
Learning as I go  .
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