[Unclenick]

Gunplummer is correct. I have a copy of the Garand blueprints and the chamber is specified as 1.282" from the barrel shoulder to the wider corner of the case shoulder counterpart in the chamber. The length of the shoulder to its intersection with the neck is not given, as the geometry of the shoulder angle and chamber neck diameters make that determination. Instead, lengths to throat and freebore and so on are given with a note as to the assumed diameter for which that length is valid. That diameter has a tolerance of +0.002", which alters those lengths when not right at the referenced minimum.

That Garand chamber and barrel thread blueprint does not specify where the bolt face would be? The bolt and chamber drawings taken together fix that dimension and the headspace tolerance. The Garand drawing is only concerned with defining a Garand barrel such that its chamber and thread timing and gas cylinder spline will make it interchangeable with all other Garand barrels without individual chamber reaming touch-up when installing it.

That is something SAAMI cannot do because SAAMI doesn't know what gun you might be putting the cartridge in? The case shoulder to barrel shoulder in a Mauser 98 action, for example, will be different than for the Garand, and so the Garand drawing is useless for figuring a .30-06 chamber for the 98. SAAMI has to specify the cartridge and chamber in a generalized way for use in all rifles, where the military drawings and gauges are concerned only with one model gun at a time.

The way SAAMI standardizes rounds is by making the manufacturer who introduces them responsible for providing the drawings and the proof loads and reference loads for that cartridge. When they have a round that was not a commercial round originally, such as military developments, or for which the original manufacturer is no longer in business, they assign responsibility to one of the existing ammunition manufacturers by agreement. That manufacturer then becomes responsible for supplying the specification and proof and reference loads to the industry.

As a result, the .30-06, like the .30-40 Krag and the .45-70, will have been put into SAAMI drawing format after the fact of the original military cartridge specifications. The new format drawings will be done so as to allow gun makers to chamber for those cartridges in different gun models. You can be sure, however, and most especially because so many military rifles chambered for .30-06 were later sporterized and used so much surplus ammunition, that following the SAAMI headspace method will provide a chamber that works with military ball ammunition, and that using a SAAMI headspace gauge will allow you to ream a chamber in a Garand or Springfield '03 variant that, when subjected to the military gauge set for the gun, will pass inspection.

One place SAAMI commercial specs and gauges fail to exactly replicate military chamber specifications is for the chamber tolerance differences in the 7.62 and 5.56 NATO rounds. You need a reamer with a longer throat and different length NO-GO and FIELD NO-GO gauges to match the military chambers for those rounds, but you can buy these. I am unaware of others.