Headspace checks

[26 Inf]

Field closing is more of an indication that your chamber is getting worn and a warning that you may need to pay more frequent attention as to how often you check to ensure the "no go" guage doesn't close.

I believe you have the FIELD and NO-GO gauges mixed up.

The NO/GO gauges are generally slightly less than the maximum chamber depth so if it closes on the NO-GO gauge you may still have some margin of safety. The field gauge is used to determine if the rifle is still safe to fire after it closes on the NO/GO gauge. If the bolt closes on a FIELD gauge the rifle should not be used.

There is a line of thinking that once the rifle is assembled and the initial GO and NO-go checks are done the only gauge you need to use is the field gauge.

[JediGuy]

So practically, you’d need all three gauges if you build and actually shoot your firearm(s).

At the same time, one would think that “the odds” favor not having to check.

[5.56 Bonded SP]

I'm just curious why you would replace the colt barrel with a BA barrel? I've owned both and much prefer the colt..
Did you turn it into an sbr or something?

(Sorry to side track)

[26 Inf]

So practically, you’d need all three gauges if you build and actually shoot your firearm(s).

Yes, I suppose that is one way to look at it. Actually, just two, if you are going to be what I would call 'prudent' and fix the rifle when it closes on the no go.

At the same time, one would think that “the odds” favor not having to check.

I believe that is also true, odds are things will be in spec if you are using new bolt and new barrel.

I keep 'build sheets' on the rifles I put together to confirm things were checked.

[sinister]

5.56mm military dimensions are generally bigger/longer than commercial .223 Remington.

GO is safe to fire.

NO-GO is absolute maximum headspace for safe operation. You generally don't want the bolt to close on a NO-GO, but if it does you should still be OK.

FIELD designates an UNSAFE headspace condition. It exceeds engineered safe fudge length and you risk case head separations and case splits. You shouldn't expect cases to do their job as gas seals at the rear of your barrel when firing.

[joeg26er]

5.56mm military dimensions are generally bigger/longer than commercial .223 Remington.

GO is safe to fire.

NO-GO is absolute maximum headspace for safe operation. You generally don't want the bolt to close on a NO-GO, but if it does you should still be OK.

FIELD designates an UNSAFE headspace condition. It exceeds engineered safe fudge length and you risk case head separations and case splits. You shouldn't expect cases to do their job as gas seals at the rear of your barrel when firing.

I would think by the time your chamber was worn to that point you'd notice your barrel is shot out and groups are getting pretty bad?
I'll start a thread called - how many rounds does it take until a No-Go gauge closes?
I remember seeing the AK Operators Union videos that show some AK's close on the no-go around 3 to 5,000 rounds

[M4C]

I would think by the time your chamber was worn to that point you'd notice your barrel is shot out and groups are getting pretty bad?
I'll start a thread called - how many rounds does it take until a No-Go gauge closes?
I remember seeing the AK Operators Union videos that show some AK's close on the no-go around 3 to 5,000 rounds

Quality AKMs, and quality ARs, should not close on a no-go in as few as 3000 to 5000 rounds.

[SiGfever]

I'm just curious why you would replace the colt barrel with a BA barrel? I've owned both and much prefer the colt..
Did you turn it into an sbr or something?

(Sorry to side track)

Just wanted a different contour, the "Hanson" profile just handles better, imho. I am not a fan of the "Government" profile.

[Todd.K]

Time for another PSA from Todd.K on headspace.

Insist on buying only gauges THAT HAVE THE ACTUAL HEADSPACE NUMBER on them. It removes the unknown and allows for an intelligent conversation about headspace.

[26 Inf]

Time for another PSA from Todd.K on headspace.

Insist on buying only gauges THAT HAVE THE ACTUAL HEADSPACE NUMBER on them. It removes the unknown and allows for an intelligent conversation about headspace.

Forster and Clymer both list the numbers on them. Depending on how often they are used those markings wear off.

IMO the Clymer Gauges I have are better marked, on both the body and the container, than the Forster gauges I own.

In my experience shotgun go/no-go gauges wear off quickly, I haven't used my 5.56 gauges nearly as much, so I can't say how much use. Probably not going to be an issue with infrequent usage.

The shotgun no go we marked with orange paint on the base, I would hesitate to mark a rifle gauge with paint on the base or on the sides - maybe a sharpie, but not paint.

Just to be safe, take a little more time and replace the go gauge in it's tube before you get the no-go out. That way if the numbers wear off you won't get them mixed up. Make sure the dimension is marked on the case - as I said the cases Clymer gauges come in are clearly labeled, my Forster gauges came in unmarked square tubes.