When very high pressures are encountered, the brass wall either spreads or blows out, and the gas under high pressure gets loose and wrecks things. This is the weak point of the M 1903 Springfield, the M 1917 Enfield, the M 98 Mauser, and other high powered rifles using rimless cartridges. 1485 inch in other words, there is a space of well over an eighth of an inch where the pressure is held only by the brass.
In the Springfield rifle the head of the cartridge case projects out of the rear end of the chamber a distance of from. One thing made evident by these tests is the fact that the weakest feature of most modern military actions is the cartridge case itself. Such rifles should be regarded as collector’s items, not “shooters”. In addition, any bolt marked “N.S.” (for nickel steel) can be safely regarded as “high number” if obtained directly from CMP (beware of re-marked fakes).ĬMP DOES NOT RECOMMEND FIRING ANY SPRINGFIELD RIFLE WITH A ”LOW NUMBER” RECEIVER. All original swept-back bolts are definitely “high number”. High number bolts have “swept-back” (or slightly rearward curved) bolt handles.Ī few straight-bent bolts are of the double heat-treat type, but these are not easily identified, and until positively proved otherwise ANY straight-bent bolt should be assumed to be “low number”. All “low number” bolts have the bolt handle bent straight down, perpendicular to the axis of the bolt body. Generally speaking, “low number” bolts can be distinguished from “high-number” bolts by the angle at which the bolt handle is bent down. The bolts from such rifles were often mixed during rebuilding, and did not necessarily remain with the original receiver. During WWII, however, the urgent need for rifles resulted in the rebuilding and reissuing of many “low-number” as well as “high-number” Springfields. In view of the safety risk the Ordnance Department withdrew from active service all “low-number” Springfields.
Those Springfields made before this change are commonly called “low-number” rifles. All Springfields made after this change are commonly called “high number” rifles. This was commenced at Springfield Armory at approximately serial number 800,000 and at Rock Island Arsenal at exactly serial number 285,507. To solve this problem, the Ordnance Department commenced double heat treatment of receivers and bolts. It proved impossible to determine, without destructive testing, which receivers and bolts were so affected and therefore potentially dangerous. M1903 rifles made before February 1918 utilized receivers and bolts which were single heat-treated by a method that rendered some of them brittle and liable to fracture when fired, exposing the shooter to a risk of serious injury.
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