Pedersen Rifle - Description and Operation

Description and Operation

The Pedersen T1E3 rifle was made in two versions: an infantry rifle with a 24 inch barrel, full-length stock with an M1903-type front band, 44 inches long (twenty made); and a cavalry carbine with a 21 inch barrel and half-stocked liked the Krag-Jørgensen cavalry carbine (five made). An unknown but larger number of infantry rifles were made by Vickers-Armstrong in Britain. The infantry rifle had a planned weight of 8 pounds, 2 ounces; weights of the rifles actually tested by the Infantry Board averaged out at 9 pounds, 2 ounces. The walnut stock had a semi pistol grip of rather shallow contour and a pronounced drop at the butt with a long cheek rest formed on top of the butt. A ventilated metal handguard covered the barrel only between the receiver and the lower band. Under the handguard was a thicken section of the barrel machined with 12 spiraling grooves, the whole design evidently intended to provide both heat sink and radiant air cooling effect. (The metal handguard was a point of criticism during Army tests due to it becoming too hot to the touch after moderate firing; the lack of uniform wood covering of the barrel was judged the cause of accuracy problems due to uneven expansion of the hot barrel). The built-in ten round magazine included a steel lower body that protruded below the bottom of the stock approximately one inch ahead of a conventional milled steel trigger guard; this magazine body had smooth and distinctive contours that reflected both the shapes of the feed mechanism parts and the designer’s evident concern for the soldier’s ease of use and safety. The front sight was an unprotected M1903 blade; the rear sight, mounted at the extreme rear of the receiver, was a protected peep sight of original design adjustable for windage and elevation. The receiver was entirely open on top between the barrel ring and the rear sight mount. The stubby, flat operating handle for the toggle joint breech mechanism protruded to the right from the forward part of the crank (the rearmost part of the breech mechanism).

The breech block mechanism was made in three parts. From front to rear they were:

1. The breech block head; this part actually supported the cartridge base.
2. The body; this was linked to Number 1 and Number 3.
3. The crank; this was secured to the rear of the receiver with the hinge pin.

The Pedersen rifle operated on the hesitation blowback principle: energy released by firing a cartridge immediately caused the breech to start moving rearward, but mechanical leverage built into the mechanism caused the actual opening of the breech to be delayed long enough so that pressure within the barrel would fall to a safe level. This was achieved with a bearing surface machined onto the front end of the crank. As the case head pressed on the breech block head and forced it to move rearward (as guided by contact surfaces in the receiver), pressure was exerted on the body, which in turn exerted pressure on the crank. The crank had contact surfaces on its rear end which would transmit pressure to corresponding surfaces in the rear of the receiver, thus relieving the hinge pin of excessive stress. As the rear surface of the body continued to exert pressure on the bearing surface on the front of the crank, the leverage exerted would cause the crank to move about 95 degrees upward from the horizontal on the fulcrum formed by it being attached to the rear of the receiver by the hinge pin. The breech block mechanism thus operated in a manner resembling the operation of the Luger pistol, but unlike that pistol the Pedersen mechanism was at no time mechanically locked. The operating principle was actually the same as that used in the Model 07/12 Schwarzlose machine gun used by Austria-Hungary during the First World War.

As with all hesitation blowback weapons, the Pedersen rifle had to have some means to prevent cartridge cases from becoming stuck in the chamber due to the relatively high breech pressure and operating velocity existing at the moment of extraction. The measure adopted by the designer was the sophisticated case coating technique described earlier, which in combination with the taper of the cartridge case sides undoubtedly contributed to the high degree of reliability noted in all Army tests. It should be noted that use of uncoated-case rounds (intentionally done in at least one test) caused the rifle to completely fail to function.

Starting with the rifle unloaded and the breech mechanism closed, the loading and operating cycle would be as follows.

1. Grasping the operating handle with the right hand, the operator would pull the crank up and back until vertical, at which point the hold open device would engage the underside of the breech block head. The breech return spring, entirely housed within the crank, would at this point be fully compressed.
2. An asymmetrical spring steel clip of ten rounds in a double-staggered column would then be inserted, feed end up, into the magazine against the spring pressure of the magazine follower; when fully inserted the clip would be caught and held by a catch. (Note: this clip, like the clip used in the Austrian Model 95 rifle, could only be inserted one way and thus could potentially cause confusion under the stress of combat). Unloading the magazine would be done by (if necessary) retracting and holding open the breech mechanism, then pushing the trigger forward from its neutral position; the clip and any remaining cartridges would be ejected upward.
3. By pulling back slightly on the operating handle, the operator would then free the breech block head from the hold open device and under pressure from the operating spring the breech block mechanism would straighten, driving the breech block head forward to push the topmost cartridge forward from under the feed lips of the clip, chambering the cartridge, and engaging the extraction groove around the base of the cartridge with the extractor. The extractor and the spring-loaded plunger type ejector were both built into breech block head. If the rifle was not immediately to be fired, the spring-loaded striker assembly (housed within the breech block head and body) could be locked by pushing the cross-bolt safety located in the breech body from right to left; this would also lock the breech block mechanism so that it could not be opened. (Army test reports identified the safety and the firing mechanism as weak areas of the T1 rifle: the safety, when applied, prevented clearing a loaded chamber and did not lock the trigger mechanism; the safety was also subject to damage. The striker was reported to have become stuck on some occasions, causing slam-fires).
4. With the rifle ready to fire, pressing the trigger would cause movement of a connector bar extending forward toward the magazine well; the connector bar movement would then cause the sear to move out of engagement with the striker and cause the chambered round to fire. (In common with bullpup rifles, which also separate the trigger from the firing mechanism, the T1 was reported to suffer from a relatively poor trigger pull feel; during at least one series of tests the connector bar broke). When the breech block mechanism cycled, the crank would momentarily block the line of sight (Army riflemen testing this rifle apparently got used to this effect quickly, but there were negative comments in the test reports regarding the crank striking the edge of the Brodie helmet then standard issue in the U.S. Army as well as damaging the brims of the felt campaign hats then worn as part of the field uniform).
5. When the last round in the clip was chambered and then fired, final upward movement of the magazine follower would engage the hold open device, which would catch and hold the breech block head in the open position; the empty clip would be ejected upward. The breech block mechanism could be released by depressing the follower and pulling back slightly on the operating handle. (The T1 and the Cal .276 Garand both had a tendency to hold open their actions and eject clips while one round still remained in the magazine).

Basic field stripping of the T1 rifle was simple: with the rifle unloaded and the mechanism held open, pressing on a stud on the underside of the crank would lock the breech return spring. The breech block head could then be guided up and out through inclined guide ways in the receiver and the crank then could be freed from the hinge pin, allowing the entire breech mechanism to be removed as a unit. The magazine housing would then be dismounted by pressing forward on the housing until the forward retaining lip would become free from the groove in the forward part of the receiver that it normally rested in and then rotating the housing downward. The entire trigger and feed mechanism group would then be removed by pressing a spring-loaded cross bolt at the rear of the trigger guard just below the stock; the entire assembly would then be freed to be pulled down and rearward to separate it from the receiver and stock. The general concept of the field stripping process is similar to that of the SKS carbine. The stock and barrel-receiver assembly would normally not be separated, following the pattern of rifles such as the German Model 98 Mauser or the Model 1903 Springfield.