7.62 NATO headspace question

[Lima Delta]

Looking at a Forster headspace gauge set for 7.62 NATO.
Apparently they make a GO gauge and a "Maximum" [field] gauge. https://www.forsterproducts.com/pdf/brochures/nato1.pdf
Curious, why no NO GO gauge?

LD

 

[Bakersfield7.62]

Probably because the spec for 7.62n has a greater range than .308 most ammo is build closer to the shorter end and if your chamber ex max feild gauge you run into excessive headspace although still in the spec for 7.62n !

 

[jonh172]

Correct me if I'm wrong, but when it comes to military designated chambers you usually only see a go and field.
Im under the assumption (my assumption only) that a "no-go" is a commercial ammo and/or chamber spec.
Probably something conjured up after a lawsuit of some sort in some period of time??

Perhaps because commercial brass is more suseptible to case head separation in longer chambers the limit range is smaller?

Commercial brass is built less robust than milspec etc...

 

[Claven2]

Correct me if I'm wrong, but when it comes to military designated chambers you usually only see a go and field.
Im under the assumption (my assumption only) that a "no-go" is a commercial ammo and/or chamber spec.
Probably something conjured up after a lawsuit of some sort in some period of time??

Perhaps because commercial brass is more suseptible to case head separation in longer chambers the limit range is smaller?

Commercial brass is built less robust than milspec etc...

Armorers would only have go and field. Third line repair facilities (i.e. small arms factories, etc.) would still use NO-GO gauges when manufacturing rifles or re-barrelling them.

 

[45ACPKING]

I have the forster go and field gauges for quick checking rifles but have them modified on the mill to allow checking headspace without disassembling the bolt. I used to carry them to gun shows or when i was doing an in person rifle purchase. Also handy at m14 clinics but for real headspace down and dirty , absolutey nothing beats the Clymer headspace gauges and for building rifles and reaming chambers to spec, the Clymer product is all i will use. I also use thier .308 match reamer for m14 rifle barrels exclusively.
Brownells sells them and you can get them in 1 thou increments as a set if you desire. These are suitable for all .308 actions/chambers.
check out brownells, not sure if any canadian retailers sell the clymer sets or singles.

 

[Lima Delta]

Correct me if I'm wrong, but when it comes to military designated chambers you usually only see a go and field.

I was wondering if maybe it was because the military uses its ammo "in the field" where chambers may tend to be a little less than spotless and maybe a no go would be too tight in the wrong circumstances...

 

[Lima Delta]

I have the forster go and field gauges for quick checking rifles

Yeah, this is what I was thinking I'd use them for too. I need to replace the bolt in my M305 which is stamped 7.62 (not 308). Was thinking if after lapping, as long as I had headspace for Nato spec ammo, I'd be fine with that (I bought a big box of Lake City just before I discovered this MIM bolt )

 

[goldenbb]

Lima Delta,
Lake city makes all of its ammo to the minimum NATO spec of 1.628 , you will have no trouble firing it out of a .308 chamber. Check your XM80 ammo and see for yourself. You don't need a sloppy chamber for modern 7.62X51 ammo. Good luck and safe shooting.


http://forums.thecmp.org/showthread.php?t=146769

https://www.canadiangunnutz.com/forum/showthread.php/901199-So-I-called-Springfield-Armory-today

http://www.fulton-armory.com/\faqs\M14-FAQs\308.htm

https://www.survivalistboards.com/showthread.php?t=8200 See post #8.

http://everyspec.com/MIL-SPECS/MIL-SPECS-MIL-C/download.php?spec=MIL-C-46931F.042098.pdf See chamber pressure on page 5.

 

[Lima Delta]

Goldenbb,
Thanks for the info. I'm not really worried about shooting 7.62 out of a 308 chamber. My concern is shooting 308 out of a chamber that maybe ends up too long after replacing the factory bolt. I'm no expert, but my understanding is that lapping in a new bolt may increase the headspace enough to take it out of spec for 308 - but not enough for 7.62. IF that turned out to be the case, I wouldn't mind if I had to forgo shooting 308 out this particular rifle. Not that I'm looking for a sloppy chamber, just looking for a contingency plan since this is to be a budget rifle and a new short chambered barrel is not an option at this point.

Cheers,
LD