One of the guns which was tested last year was (and which was being rebuilt at Springfield Armory for test this year, but was not completed in time), obtains its power from a small cap over the muzzle. The cap slides on the barrel, and has a hole in its front end large enough for the bullet to go through. When the gun is fired the bullet passes out through the hole and the gases which follow draw the cap forward a short distance. This motion of the cap is transmitted through a rod to a lever which throws back the breech-bolt, ejecting the empty shell. A spring returns the breech-bolt and cap, at the same time reloading the gun. This is called the Bang system of operation. It was patented many years ago by Maxim, and was used by Soren H. Bang as the operating principle of a rifle which he submitted to our Government in 1911. The Bang gun showed great reliability, and passed the most creditable test of any automatic arm submitted before the war.  However, it was clumsy and difficult to make, and the barrel had to be extremely small to keep the weight down. These disadvantages prevented its adoption, but nevertheless its excellent functioning through the various tests earned a high degree of admiration for the gun and its inventor. The system is extremely flexible, and will shoot high pressure or low pressure cartridges equally well in the same gun. The muzzle cap reduces the recoil about 20 percent, and cuts down the flash. It is also said to reduce to some extent the sharpness of the report. Against these good points must be set down the fact that it adds a few ounces to the weight, and makes the attachment of a bayonet difficult.

Last year Springfield Armory redesigned the Bang gun, and entered the new model in the test. The modified gun was simple, light, compact, and of pleasing outlines. It functioned well, and showed promise of success, but broke during the endurance test and was withdrawn. The board recommended that the rifle be redesigned for the purpose of perfecting it and accordingly an improved model was started but was not completed in time for the test, though work is being continued on it.

Besides the modified Bang, the Ordnance Department submitted to last year's test a second type of rifle which was built by Mr. John C. Garand, a mechanical engineer employed by Springfield Armory. This gun is operated on a novel principle originated by Mr. Garand, which was none of the disadvantages of the systems heretofore mentioned. Mr. Garand's principle of operation consists in allowing the primer of the cartridge to push back the firing pin, and in making this backward motion of the firing pin unlock and open the breech-block. At first this may seem a difficult thing to do, but when it is remembered that with the service pressure the total backward force on the primer is over 1,800 pounds, it will be seen that by making a heavy firing-pin, which just fits the head of the primer, a very short backward motion of the primer of not over 2 or 3 one-hundredths of an inch will put a large amount of kinetic energy into the heavy firing-pin, which is sufficient to operate the gun. During the test of 1920, 3,000 rounds were fired by this gun before the board, which demonstrates without question the possibility of operating a gun on this principle.

However, the test developed some structural weaknesses in the design, and this gun was also redesigned. This year's model is far simpler than the one submitted last year. However, this year's Garand gun, like the Modified Bang, was not completed in time for the test. It was first assembled and fired during the week that the board met, and as was to be expected, some adjustments were found necessary. The gun in its unfinished state was demonstrated by firing, but was not submitted to the regular test.

Work on the gun is being continued. Its light weight, neat appearance, and simplicity of mechanism have elicited much favorable comment, but of course final judgment must be reserved until after the gun is proved by an official test.

Still another rifle which shows a radical departure from the old accepted lines is the Thompson auto rifle, which was entered by the Colt's Patent Firearms Co., both in this year's test and in the test of 1920. This gun employs for its operation the Blish principle of adhesion, which was discovered and patented by Commander Blish of the U.S. Navy. This principle was first observed in working with large guns. The breech-blocks of these guns are held in place by an interrupted screw. It was observed that in firing very light charges the breech-blocks had a tendency to unscrew from the pressure on the front, while in firing heavy charges this tendency was absent, instead of being greater, as we would naturally expect. Commander Blish undertook experiments to determine the cause of this peculiarity and came to the conclusion that while the inclined surfaces would slide under moderate pressures, they would adhere and remain immovable when the pressure on them is high. Further research developed the fact that by selecting the proper angle for the pitch of the thread, a breech-bolt of the interrupted screw type could be built for the Springfield Rifle that would hold fast under high pressures and fly open under lower ones. While the bullet is in the rifle, the pressure is high enough to lock the rifle shut, but when the bullet has left and the pressure has dropped the right amount, the mechanism opens and throws out the empty shell. This is the principle of the Thompson auto rifle designed by Gen. John T. Thompson, retired, the father of the present Springfield. It goes without saying that a mechanism of this kind is free from the disadvantages mentioned as applying to the gas and recoil operated types. It remains for the board to answer the question as to whether or not a satisfactory gun is in sight as a result of the test.