Springfield 1903

[1903Collector]

"GO", "NO GO", and "Field" gages for .30-06 are what you seek. Forster was one mfr, there are/were others. (Amazon, Ebay, Midway, etc.) Normally the length of each gage is marked on the gage itself. I have learned that there are some gages with slightly different sizes (lengths). There are are USGI (Hatcher) specs, SAAMMI and CPI specs. However, as I understand it the differences are due to the physical point of the spec of each (USGI/Hatcher dims was measured to the beginning of the shoulder rather than a mid point of the shoulder, so I dont think it is an issue, just make sue you have a full set of one standard or another to avoid any confussion.

Hatcher's Notebook headspace spec for the 30-06 as minimum of 1.942" ("Go") and the "Field" is 1.950". Current Forster SAAMI spec gauges are 2.049" GO and 2.058" Field. The difference between the Min/GO and Field is 0.008" for both.

There is no such thing as a "matching" 1903 bolt to a 1903 receiver. The designs are such that all receivers and bolts across the makes and years of the 1903 rifle were interchangeable. There was no requirement to "match" a bolt to any rifle during arsenal rework and rebuild.

Having said that, I have confirmed different results in headspace measurements while using different bolts on the same receiver. I determined that this was due to the bolt itself being worn at the lugs causing slightly different distance between the engaging surface of the lug to the receiver and the bolt face (i.e., the bolt was out of spec!) This, however is rare. It is my understanding that the old tale of matching bolts for the 1903 springfield rifle is anecdotal and not based upon technical facts.

Remember, the primary cause of being out of headspace is due to the size of the barrel chamber. A "new old stock" (NOS) barrel is normally short chambered and often the bolt will not even close on the "Go" gage. Such barrels need to have the headspace cut to the minimum "G" length after the barrel and receiver have been mated. A barrel with a worn barrel chamber that closes on the "NO GO" gage is ready for replacement but still serviceable in battlefield conditions. A barrel with a worn barrel chamber that closes on the "Field" gage must be taken out of service and replaced, even in battlefield conditions.

Other causes of poor headspace are worn lug engagement surface of the receiver and the bolt, but these are very rare. Both the bolt and receiver were hardened to a higher level than the barrel, so barrel wear is the norm by a a couple orders of magnitude.

[ssgross]

However, as I understand it the differences are due to the physical point of the spec of each (USGI/Hatcher dims was measured to the beginning of the shoulder rather than a mid point of the shoulder

I don't think this difference in chamber dimensions came into being until the m1. The datum point is just a relative reference. If you check headspace of an m1 with its original barrel with different gauges, you will see the bolt is just a hairs-width or less from closing on a forester no-go gauge, maybe two hairs with a clymer no-go. On similar condition 1903's, with both these gauges the bolt falls way short of closing. I have confirmed this first hand. The USGI M1 chamber was carefully designed to minimize failures under combat conditions and aid in the prevention of out of battery discharges (in conjunction with the design of the rear of the firing pin). The short version is that the chamber intentionally had some slop. CMP has an article explaining this too - and states the clymer gauge is the closest in spec that is commercially available.