Switzerland's finest the Karabiner 31 K31

Guns Magazine, June, 2004 by Holt Bodinson

Often referred to, and probably wrongly so, in surplus circles as a Schmidt-Rubin, the Swiss K31 is a jewel of the gunmaker's art. Selling for between $109 and $125, the service grade K31s currently available on the surplus market are the finest quality military rifles ever to hit the streets at those prices. Just a few years ago, you couldn't touch a K31, if you could find one, for less than $350. At the time, even that was a bargain price.

Like the beautiful Swedish Mausers, the Swiss K31s never had to do battle, were meticulously maintained by Switzerland's citizen soldiers, and consequently have arrived on our shores in very good to excellent condition. Better yet, inexpensive, match grade, Swiss surplus ammunition has finally caught up with the guns, and we're now able to see just how well these rifles can perform.

What's interesting from a historical point of view is the Swiss, like the British with their Enfields, kept a basic rifle design in service for a very extended period of time. The Swiss first fielded the Schmidt designed rifle in 1889 and with a few modifications, continued to produce it into the 1960s. The Schmidt design was not officially replaced until 1958 when the select fire and racy looking Sturmgewehr 57 was adopted. Total production of the K31 is estimated at over 500,000.

Pioneering Work

The original Model 1889 evolved as the result of the work of two Swiss Army officers--Lt. Col. Eduard Rubin, Director of the Swiss Federal Ammunition Factory and Research Center at Thun, and Major Rudolf Schmidt, Director of the Swiss Federal Arsenal at Bern.

Lt. Col. Rubin's contribution was the design of a small-bore (7.5mm caliber) cartridge featuring a jacketed, lead core bullet. This was a radical design for the era. Many credit Rubin's pioneering design work to be the origin of the rimless case, the boat rail bullet, and the metallic jacketed bullet. That's quite a tribute.

Major Schmidt was a student of military firearms design. After completing an exhaustive study of contemporary models, he designed the Model 1889 Schmidt rifle that featured a straight pull bolt action and a detachable, steel, 12 round magazine.

The Schmidt straight pull action is remarkable. It is complex. It requires exceptionally precise machining, but it is fast to operate. I have never heard or seen anything in print regarding the rate of fire a proficient Swiss citizen soldier could sustain, but it must have been impressive indeed, particularly with 12 rounds available in the magazine. I suspect the very thought of it kept more than a few potential foes at bay.

If you pick up a Schmidt-Rubin and operate the bolt without any ammunition in the magazine, the bolt will seem stiff and jerky--simply awkward. Load the magazine with some ammunition though, and things change. Suddenly, the operation is slick as grease.

Complex Construction

We normally think of the bolt of a bolt action as a single unit containing integral locking lugs. Not so, in the Schmidt-Rubin. In very general terms, the Schmidt bolt itself is actually composed of three major interrelated parts: An inner bolt incorporating the bolt face and extractor that feeds and extracts the cartridge, a striker assembly, and an outer, rotating locking sleeve that actually carries the locking lugs.

The outer bolt locking sleeve is milled with a helical groove. The bolt handle assembly features a stud that rides in the helical groove and further into a slot in the inner bolt. The bolt handle assembly itself rides and cycles in a straight groove or housing formed inside the right receiver wall of the action. When the bolt handle is pulled straight back, the stud of the bolt handle assembly riding in the helical groove causes the rotation and unlocking of the outer locking sleeve and the cocking of the striker, ending with the extraction and ejection of the fired case. You really have to hold and cycle a Schmidt to understand just how unique this action is.

The bolt assembly was re-designed three times during the lifespan of the Schmidt-Rubin rifle and provides an easy way to determine which model you're dealing with. The original 1889 bolt featured a locking sleeve with the locking lugs located at the rear of the sleeve and a long, protruding bolt. The strength of this system was sufficient for the early Swiss 7.5x53 GP (Gewehrpatrone) cartridge loaded with semi-smokeless powder.

In 1911, a high pressure, smokeless 7.5x55 GP cartridge was adopted and the locking lugs of the Schmidt-Rubin rifle were moved from the rear of the locking sleeve to the front of the sleeve while still retaining the action's rather distinctive long bolt. The magazine capacity of the new Model 1911 was reduced to 6 rounds.

The Model 1911 Schmidt-Rubin rifle was widely imported into the United States in the 1950s and 1960s. I remember seeing a number for sale that had been sporterized and converted to .308 Win., which brings up an interesting point.

Rare Variations

A number of new K31 target rifles filled with elegant diopter sights and chambered for the .308 Win. were imported into the U.S. and occasionally appear on the used market. I came across one recently in Murphy's gun store in Tucson, Ariz. The price was $1,050. That's one of the reasons I consider the current crop of K31s priced at less than $150 such an incredible bargain.