When the ring is pulled back far enough to allow the rectangular tab to rotate and rest on the flange, the rifle will not fire, but the bolt can be operated. This fairly mild load used a round nose bullet of 210-grains at around 1,970 feet per second.Īt the rear of the bolt is a large finger-pull ring that serves as both the safety and a manual cocking/decocking device. The models with the lugs near center for the earlier, lower pressure version of the 7.5 round allowed the bolt to compress and thus would not tolerate much more pressure than was present with the M90 loading. These changes in 1931, part of a modernization program for the rifle, made the new bolt both shorter and stronger. The K-31 bolt differs from earlier models in that it is shorter and has its locking lugs forward near the head of the bolt sleeve whereas the earlier models had the very long bolt with lugs nearer the center of the body. The actual turning of the lugs is accomplished by means of an actuating rod on the side of the bolt sleeve that engages a helical or spiral groove in the sleeve which forces it to rotate as it is moves back and forth. This simply means that instead of lifting the bolt handle to turn the bolt lugs out of their locking recesses, the Schmidt-Rubin bolt is merely pulled straight back to accomplish the same thing. The cock-on-opening design, while it is a bolt action, is somewhat unusual in that as opposed to the more common turnbolt style action most are familiar with, this rifle is of the so called straight-pull design. On a historical note, in the 1930s, the Swiss Guard at the Vatican was issued one hundred K-31 rifles, making the Vatican the only other “Sovereign Nation” to be issued Schmidt-Rubin rifles. The round would evolve into the longer 55mm case for the later Gewher 1911 model rifle and carbine, and then continue on into the last rifle of the series, the K-31. The cartridge would eventually be adopted as the 7.5×53.5 for use in the M1889 rifle, the first of the Schmidt-Rubin service rifles. The Vetterli rifle was not a strong enough design to handle the increased pressure of the newer center-fire round. The cartridge the K-31 is chambered for, the 7.5×55 Swiss, was, like the rifle itself, a final version but of a design by Eduard Rubin, that had originally been experimented with in the Swiss service rifle that predated the Schmidt-Rubin design the 1869 Vetterli 10.4×38 rimfire rifle. The rifle’s designer, Colonel Rudolph Schmidt, offered his design to the military while employed as a weapons technical officer at the government arsenal in Bern. That rifle, the Karabiner 1931, or K-31 as it is commonly known, was like its predecessors – a straight-pull bolt action design that to many American shooters may seem a little odd. Between the years 19, the final incarnation of the Schmidt-Rubin rifles that began with the M1889 Infanterie Gewehr, was built at the Eidgennossische Waffenfabrik in Bern, Switzerland.
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