The Japanese Pedersen

Vickers-Armstrong Pedersen Self-Loading Rifle
   .276 cal

Pedersen T2-E1 Semiauto Prototype rifle
Caliber .276Pedersen
Magazine 10-shot
manufactured by Vickers-Armstrong

Petersen Semi-automatic Rifle Mechanism

The Pedersen rifle was a self-loading rifle using a toggle-locked breech, waxed cartridges, and a 10-round magazine fed from en-bloc clips. Designed by John Pedersen and chambered in .276 Pedersen, it made an unsuccessful bid to become the standard rifle of the US Army, rejected in favor of the M1 Garand. It was also trialed by the British, who were impressed but rejected it primarily on account of the waxed cartridges. The wax cartridges were thought to be a problem in the tropical areas of the far-flung British Empire. Vickers was involved with making these samples, and so it is also known as the Vickers rifle (though the rifle design was unchanged).

When the Army Ordnance folks conceived of the idea of developing a semiautomatic rifle just after World War I, they very intelligently hired two top-notch gun designers for the job--John Garand and J. D. Pedersen. It was much slimmer and trimmer than the .30-'06 Ml, about a pound and a half lighter, and generally handier. Recoil were quite mild, and its magazine capacity was 10 rounds instead of eight. While the .276 Pedersen was less powerful than the .30-'06, it was more than adequately powerful for service rifle use--typically launching a 125 grain 7mm bullet at 2,550 fps.

In 1932 the recommendation for adoption and production of the .276 Garand rifle was approved all the way up to Army Chief of Staff, General Douglas MacArthur. Unfortunately, MacArthur unilaterally disapproved it. He wanted the rifle but in .30-'06. This was done and the .30-'06 Garand eventually passed its tests just as well as did the .276 version.

The .276 Pedersen round was an experimental 7 mm cartridge developed for John Pedersen's Pedersen rifle, a competitor to the M1 Garand Rifle (neither are technically related to the Pedersen device). Developed in 1923 by the United States, it was intended to replace the .30-06 Springfield in new semiautomatic rifles and machine guns. When first recommended for adoption, M1 Garand rifles were chambered for the .276 Pedersen, which held ten rounds in its unique en-bloc clips. The .276 Pedersen was a shorter, lighter and lower pressure round than the .30-06, which made the design of an autoloading rifle easier than the long, powerful .30-06.

The US Army Chief of Staff Gen. Douglas MacArthur rejected the .276 Pedersen Garand in 1932 after verifying that a .30-06 version was feasible. Because of the factors of Depression era budgets, existing tooling and stockpiles, a caliber change was probably ill advised.


Opened Action
Petersen Semi-automatic Rifle Mechanism

About the year 1927 Mr. J. D. Pcdcrscn perfected a semiautomatic rifle on the retarded blow-back principle,
which rifle gave an especially a:isfactory account of itself in trials. It also has a crank and connecting rod as
does the Schwarzlose gun, but the mechanical arrangement  is somewhat different.

The operation of the Pedersen rifle is shown in Fig. 3. A is the breech block which is held against the head of the cartridge by the blocks B and G which are in line with each other and which transmit the thrust of the breech block to the heavy pin, D, which goes through the receiver. These three parts, A, B and G, form a toggle joint, and C, the point of contact  between B and G, is just slightly above the line of thrust between the head of the cartridge case and the pin, D. Thus when there is a very heavy pressure on the front end of the breech block, A. There is tendency for the toggle joint to "break" and the piece, B-G, to move upward as shown in the cut marked "After Firing."  If the point of contact at C were directly on the line of thrust, the toggle joint would remain locked and the breech would not open, but at this point, C, is just above the line of thrust the breech does fly open as soon as the pressure comes on the head of the bolt, but this opening is retarded because the two pieces, B-G, roll on each other in starting to open in such a manner that the contact point, C, continues for some little time to remain near the line of thrust. The shape of the  rolling surface is worked out very skillfully in order to insure this result. As the breech opens the spring, F, is compressed and as soon as the motion is completed this spring causes the breech to close again.

However, like the Thompson gun, this mechanism starts to open while the high pressure is still on, and therefore it was necessary to lubricate the cartridges. Instead of lubricating them with oil, each cartridge was coated with a very thin film of hard wax which had avery high melting point, so that the cartridges would not pick ip dirt when dropped as they would if oily or greasy.

There was a good deal of talk about the disadvantage of  "lubrication" in this gun, but after all it seems that this disadvantage is

more fancicd than real, as the cartridges are not greasy or oily.  Moreever, it has been found that corrosion is one of the greatest auses of season cracking in brass cartridge shells, and if this wax prevents the cartridge brass from corroding it may be quite possible  that would eliminate deterioration of cartridges from season cracking.


Up to that time, all the seiui-aumnuatic rifles submitted for test had been rcquired to be of .30 caliber, adapted to use the service cartridge. M. Pedcrsen presented very convincincr arguments to the effect that the .30 caliber cartridge was more powerful than
required for the shoulder rifle, and that to reduce the caliber 'to the  ballistically ideal 7 mm or .276 would result in a number of
advantages, to wit; saving in weight; saving in material, reduction of heating  in rapid fire; ability of the soldier to have a larger number of cardridges available; etc.

The  Army made an extended study of this question, including a series of firings at live animals with .256, .276, and .30 caliber bullets.  It was found that the .256 was apparently the worst killer, on account of the fact that the bullet had less diameter, hence less  gyrostatic stability, and would yaw badly upon impact, and make very lethal wounds. The .276 was found to be about as effective, and as it had certain advantages over the .256, its adoption was decided on for the new semi-automatic rifle that it was hoped would soon be adopted.

The cartridge selected had been designed by Mr. Pedersen with features making it especially suitable for automatic firearms, such as an increased taper for easy extraction. The ammunition was first made with a solid bronze bullet weighing 125 brains; later with a 126 grain jacketed boat tail bullet. The bullet diameter was .2845. The charge was about 30 grains of duPout IMR No. 25. At one time a small lot of this aniniunition was made with flat base bullets.

The Pedersen gun was made with what is called the block clip. This is an arrangement whereby a packet of ten cartridges is shoved bodily into the magazine, clip and all. After firing ten shots, the clip automatically jumps out of tile rifle and the bolt stays open, ready for the next clip to be inserted.

After the Pedersen rifle, using the special .276 caliber cartridge designed by Mr. Pedersen, had successfully passed the severe Army tests, it seemed on the point of adoption bv our armed forces; but a high command decision was made not to change the caliber of the service cartridge, and the final action to adopt this gun was never taken.