Check headspace???

[coolcraigster]

I have sets of Forster gauges, Go, No Go, Field. If you purchase headspace gauges, do not mix brands.

I'm kinda confused on the field gauge still. So it should close on the GO gauge, shouldn't close on the NO GO gauge. So if it closes on NO GO it fails correct? Why is there another gauge (Field) past NO GO if its not even supposed to close on NO GO?

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[Todd.K]

Go and No-Go are used for manufacturing a rifle or replacing a bolt or barrel.

Field is the max before being considered worn out or unsafe. It doesn’t really happen with modern designs and metallurgy much.

A picture is worth a thousand words here.



https://www.forsterproducts.com/pdf/...2018_print.pdf

Not quite accurate.

SAAMI is 1.4636” to 1.4736”, though it’s unlikely anything is actually made near the high limit.

Acceptance requirements for the M16/M4 is 1.4656” to 1.4706”.

The second is what a new AR should measure, so get gauges with the actual number on them or from a manufacturer that states what size their Go and No-Go are.

[coolcraigster]

So do yall recommend just getting GO and NO GO gauges or getting the Field gauges as well? I have 556 and 223 wydle chambers. Im guessing one set of gauges will work for both??? Also have a 300 BLK.

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[gunnerblue]

So do yall recommend just getting GO and NO GO gauges or getting the Field gauges as well? I have 556 and 223 wydle chambers. Im guessing one set of gauges will work for both??? Also have a 300 BLK.

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https://www.m4carbine.net/showthread...6-go-no-gauges

Here's a thread from back when Iraqgunz was still with us. Good info.

The field gauge tells you that your chamber is unsafe and is, still I believe, the only gauge used by the military.

Also, checking headspace with a fully assembled bolt can give a false reading due to the spring pressure of the ejector

[T2C]

What about for WYLDE chambers...are there gauges for those?

I use regular .223 gauges.

[prepare]

[QUOTEThe field gauge tells you that your chamber is unsafe and is, still I believe, the only gauge used by the military.

Also, checking headspace with a fully assembled bolt can give a false reading due to the spring pressure of the ejector[/QUOTE]
81580D9F-B92A-443E-8342-32E6A8E3039F.jpg

If you have check head space frequently turning or having your gauge turned so you don’t have to strip the bolt is a huge convenience.

[Todd.K]

I have 556 and 223 wydle chambers. Im guessing one set of gauges will work for both??? Also have a 300 BLK.

5.56 and any .223 chamber all headspace the same. The difference is in the neck and throat, while headspace is where the shoulder is set.

300 BLK will need to use 300 BLK gauges.

[lysander]

For those curious about belt fed head space.
M249 SAW GO 1.4940" - 1.4947"
M249 SAW NOGO 1.4980" - 1.4982"
M249 SAW FIELD 1.50196" - 1.50216".

This is wrong, or at least, very misleading.

The M16, C.I.P., and SAAMI all use a 0.330" reference diameter for measuring headspace. For unknown reasons, FN uses a 0.300" reference diameter for measuring headspace, so they appear longer.

They are actually shorter. If you measure the M249 gauges to a 0.330" reference diameter you get these dimensions:

M249 SAW GO 1.4609" to 1.4611"
M249 SAW NOGO 1.4647" - 1.4649"
M249 SAW FIELD 1.4686" - 1.4688"

You might note that all of these are a good bit shorter than an M16 or SAAMI .223

[Red*Lion]

It is ideal to have all three gages. GO, NO GO and Field. The Field is important if the NO GO gage goes. The Field gage as already said will tell you if the rifle if safe to shoot. As long as the Field does not go, then you are safe to shoot. Some manufacturers like Faxon even state that it is not uncommon for the NO GO gage to go and that the barrel is still good to go as long as the Field does not go.

[Disciple]

This is wrong, or at least, very misleading.

Surprising given the credentials of who I quoted. Correction noted. Why is the M249 chamber shorter?