Go / No-Go guage question.

[skeeter]

OK, I received my BCG in the mail this afternoon, its a standard DPMS bolt with a chrome carrier.

This being the first assembly where I secured the bolt and barrel from two different sources. I was assured by the barrel maker the headspace would not be an issue if I used a standard DPMS bolt. That said, I went ahead and purchased the "go, no-go PTG Forster guages" so I could check things for myself prior to fire testing. Thing is the bolt will go into battery on either guage, however it takes a good bit more pressure to close on the no-go guage.

Is it possible to use too much force when using this type of headspace guage and thus return a inaccurate result?

Cheers!

[Jgun]

You did strip the bolt first right? Is it possible that you've got bad gauges on your hands? Have you tried the gauges in any of your other 7.62 rifles with matched barrels/bolts? Checking with a stripped bolt.

[skeeter]

You did strip the bolt first right? Is it possible that you've got bad gauges on your hands? Have you tried the gauges in any of your other 7.62 rifles with matched barrels/bolts? Checking with a stripped bolt.

Answer to question #1.

I did strip the bolt, I have also measured the guages. The go gauge is marked 1.630, and the no-go is marked 1.634. Thing is I only measure a difference between the two of about .002, not .004 as is listed on the guages. I can feel just a slight bit of movement with the go guage, but absolutley no movment at all with the no-go. Please excuse my ignorance here, but is .002 that big of a deal in this case?

Answer to question #2.

This is my first and only .308 Winchester, my other AR's are 5.56 and 6.8. I either purchased a complete upper or bought the barrels and had them headspaced with a bolt from the same manufacturer. I didnt have any tools or experience and figured that stuff was better left to those that know what they are doing. But after putting those guns together and reading several threads on various forums I figured what the heck do it all my self and get some OJT. So here we are, learning by expirence.

I appreciate you guys' input.  8)

[skeeter]

Correction.... I listed it as PTG guages, they are actually Forster.

Anyway, I decided to go out to the Forster site and do some more reading. If all else fails, read the directions.

According to Forster even if the bolt locks on the no-go guage it may still be within SAAMI tolerances, and will be servicable but recomends you should check with a Field guage.

Well I dont have a field guage, so I figure as gnats hair tight as the no-go guage is I think I'll be fine. So tomorrow I will check with a couple live fire tests. I read that with accuracy might be compromised with a loose headspace. Guess we shall see. ;)

[Jgun]

If the stated range between the two gauges is supposed to be .004" and, assuming you measurements are correct, they actually only differ by .002", I think that would qualify as being a set of out of tolerance gauges. If, as you say, the no go barely fit's, the likelyhood is that if it were .002" longer, it wouldn't. You know, your measurements are only as accurate as the gauges/measuring devices used to check them, That's why machine shops doing military work have all their gauges calibrated periodically. I've heard that the PTG gauges are very good in this regard.

[survivalshop]

You should not be putting any thing but very light finger pressure to test for head space. That means one finger .

You need to remove the ejector , the extractor can stay in most new gages.

It is true that you may be able to fit both go & no go gages in the chamber with force.

If its a 7.62 chamber , both will fit any way. One will be tighter as you have found out .

[skeeter]

I have ordered a Field guage to verify but after shooting the gun yesterday it functioned great. Not a single problem.