Putting together a couple of retro rifles.  Do I need the 223 or 5.56 headspace gages?  I already have a 223 field gage.

Here is a letter I got from Clymer regarding the differences between 5.56 and .223 gauges:

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]


Short answer, in GO and FIELD the 5.56 and .223 are the same and only the NO-GO are different.  So, depending on what your rifle barrel is chambered for you need a GO in either 5.56 or .223 and a NO-GO in the proper designation.
A field gauge IMO is really quite useless.  If it closes on a NO-GO that is all I need to know and it is time for some work.  If it closes on the GO and does not close on the NO-GO, all is well.  I really don't see the reason for a FIELD for the average person.  And if it does not close on the GO, there may be problems with some ammo not chambering.  My 6.5 Grendel will not close on a GO but it has chambered everything I have fed it so far.  However, if it were a serious use rifle and it would not close on a GO I would be looking at swapping bolts or some other modification until it did close on a GO.

Thanks for the info.

if the bolt closes on a no go gauge what are you suppose to do then?

It can close on a no go but shouldnt close on a field guage

If it closes without anymore effort than closing on a GO gauge, AND it is a new barrel assembly; you have the choice of sending it back or keeping the boo-boo. However unless the manufacturer has a good reason to cut their chambers so loose and offer it as a brand new barrel; it really IS a factory made boo-boo.