Headspace soul-searching: 308 vs 7.62 NATO

[Lloyd Smale]

odd you had trouble with military ball. Its usually loaded to lower pressures then factory 308 stuff is.

[oconeedan]

With all of the technical issues aside, my FR8 is one of my favorite rifles. It has never had any issues with any factory ammo, and it is a great cast bullet gun. It has also proven to be a good hunter.
Hey...it's a large ring Mauser, kinda hard to not like that!!

[nicholst55]

That is not correct regardless of what Gus claims.

Most if not all US manufacture use the U.S. Sporting Arms and Ammunition Manufacturers’ Institute (SAAMI) spec'ed chambers and gauges. They can be found here. https://saami.org/technical-informat...ami-standards/

Permanent International Commission for Firearms Testing – commonly abbreviated as C.I.P. or CIP is the European Equivalent of SAAMI but there are differences. https://www.thefirearmblog.com/blog/...ivalent-saami/

The third is the NATO—EPVAT (Electronic Pressure Velocity and Action Time) firearm regulatory organization. They seem to align more with CIP than SAAMI. The 5.56 and 7.62 x 51 will conform to this standard. The 308 Win and the .223 Rem will conform to SAAMI standards.

Forster gauges are purchased either as SAAMI or NATO. If they do not meet the tolerances that is a QC issue. https://www.forsterproducts.com/prod...adspace-gages/

Before I retired I would inspect all my gauges and reamers on a 100X optical comparator and I did find some GC issues with some other brands, however, out of the 2 dozen or so Forster I have not found any out of spec. That includes the Forster gauges that were used on team firearms and yes they had to be calibrated through the PMEL lab (Precision Measurement Equipment Laboratory (PMEL) is a United States Air Force (USAF) facility in which the calibration and repair of test equipment is accomplished).

I have the Forster .001" step sets in .223, 308 and 30/06 plus miscellaneous other go/no go gauges in other calibers.

On a side note in 25 plus years of having PMEL do the initial calibration of precision inspection equipment like gage blocks, indicators and mics. the percentage of fails was surprising high. It took me 3 sets before I had a serviceable set of Starrett Webber gage blocks.

Whether Gus is correct or not, that is what he stated in that thread. I have also had a number of brand new gages rejected by the Army's TMDE (Test, Measurement, and Diagnostic Equipment) folks. I had two brand new M14 test bolts red-tagged (condemned) when I sent them in for certification the first time. I suspect that there is a disconnect between the drawing tolerances from the time that they were manufactured, to the time that they were certified. Tolerances do change over time.

[popper]

my dilemma
If you reload, HS is not a problem, set it with your sizing die. Short cases will blow out the shoulder when fired. If the action is stretched, that does need fixing.
Definition - cae gauge. steel with a large hole for body, small hole for neck (bottleneck case). Slight fraft step at junction set a DATUM point. Probably SHOULD be halfway between both hole dia.s. It is probably nothing like your gun's chamber! All it measures is case rear to datum point. Yes, if neck is too long it will show. I have 3 wilson gauges, 308,30/30 & BO. Most factory ammo is correct as they use OPTICAL scanners to verify each case. Monitor to check when the equipment needs to be adjusted. You can check the difference between unfired and fired. Not against gauges but they can't fix you ammo.

[cwtebay]

I have a Spanish FR8 (large-ring Mauser action), which I purchased as a general purpose hunting/plinking rifle. I've fired all manner of surplus and commercial ammo through it, to include my various reloads, and not had any issues, save some minor sticking of the bolt with one particular lot of German surplus 7.62x51. Nevertheless, I decided to purchase a .308 Winchester field gauge. Now I was/am aware of the dimensional difference between NATO and commercial chambers, but there is an overlap, and if it passed a commercial field gauge, then it would obviously pass a NATO max chamber gauge. Alas, the bolt closed easily upon my new Forster gauge. I now have a NATO gauge on the way. So, here's my dilemma:

If the rifle passes the NATO Max gauge, do I really need to stop shooting all commercial ammo? Or is that all made to the same specs anyway?

If she fails the Max gauge, what would be my best option in regards to having the headspace fixed? The neck-size-only method is not acceptable, as I like to use this thing as my 30-caliber garbage disposal. For reference, the 308 Field gauge is 1.638", and the NATO Max gauge will be 1.6455".

A question I've thought about since you posted - what sort of age do your German cartridges bear?
The reason I ask is based on powder "break down". Example: if you load with stick powder and subject it to age, abuse (dropping, shaking, etc) you can change the burn profile of that powder and thereby change the pressure curve.
I recall learning that with 303 British milsurp with cordite in my early 20's, and some 35WSL ammunition more recently.
I'm quite certain that one of the powder guru's on this forum can answer whether or not that could be your issue.

Just a thought.

p.s. yes, I am aware cordite is a whole other kettle of fish.....

[samari46]

I have a Remington 40x stainless steel single shot rifle. Normally I would figure that it would be chambered for the 308 Winchester. But stamped on the barrel is 7.62 NATO. Go figure. Frank