18 ammunition only under perfect or constant atmospheric conditions It is believed that a much more satisfactory determination and comparison can be arrived at by taking a mean of the mean vertical deviation and the extreme vertical deviation, this mean to be known as the "vertical error." The board is of the opinion that the present type of machine rest does not permit the rifle to work under conditions best conducive to accuracy; that in an ammunition test, where it is desired that the accuracy or inaccuracy of the ammunition stand out as far as possible alone, a much more satisfactory method of testing can be devised; that the only satisfactory method of testing the service rifle is by extended firings of the rifles as they are intended to be used by expert shots using ammunition of known accuracy. The board is of the opinion that a much more satisfactory machine rest for testing ammunition can be devised by following in general the type of rest known as the "V rest," and described by Dr. F. W. Mann in his work "The Bullet's Flight" (Scientific American, 1911). This rest consists of a heavy steel V-shaped trough, considerably longer than the barrel, adjustable for elevation and azimuth and secured to a concrete base. The barrel of the rifle alone is used in testing. The barrel rests in the forward portion of the V-shaped trough in concentric maple rings, and is provided with a concentric action. Upon being fired the barrel slides straight backward in the V until it comes to rest. There is absolutely no jump to the barrel, the unequal restriction of which is so conducive to inaccuracies in other types of rest. Barrels for use in such a rest should be very heavy, should be provided with concentric rings of maple which hold the barrel in line with the axis of the V, and should also be provided with a concentric action so that the mass of the breech is directly behind the axis of the bore. These barrels should be most carefully bored and rifled, straight without hammering, and of the standard dimensions as to grooves and lands and as to bore and groove diameter. The chamber particularly should be exactly in line with the axis of the bore, and should be cut with only the minimum tolerances made necessary by the tolerances of the ammunition to be tested. When it is desired to conduct a machine rest test with complete service rifle, it is believed that it would be better to so design the machine rest as to secure only the butt and receiver of the rifle, leaving the barrel free to jump and vibrate as it will. Also that the rest should be so arranged that in recoil the rifle will slide to the rear and will come to rest of itself in approximately 5 inches of 19 travel. There should be no springs or weights to return the slide to the firing position. The board is of the opinion that the present rifle does not perform at its maximum efficiency as to accuracy until approximately 150 rounds have been fired from it, and recommends that hereafter that number of rounds be fired slowly from barrels which are intended for testing ammunition before record groups are started. The board is of the opinion that the present method of extreme rapid fire for each group of 10 shots is not conducive to the best accuracy and is entirely unnecessary if the method of measuring groups known as the "vertical error" and recommended in this report is adopted. That the rifle should be used as a single loader, each cartridge being fully seated in the chamber by hand before the bolt is closed. The trigger should be pressed by squeezing between the rear of the trigger guard and the front of the trigger, or with a concentric action there should be a pneumatic release with bulb and tube. Other than as indicated, the hands or body should not touch the rest or rifle at the time of firing The board is of the opinion that to best fulfill its duties it should meet again at the conclusion of the national matches for the purpose of considering the results secured in these matches with the ammunition and rifles which it has recommended, and it does therefore adjourn to meet at the call of the senior member thereof. All the members of the board have concurred in these proceedings. TOWNSEND WHELEN, Approved: B. CROWELL, Lieutenant Colonel, General Staff, President. Captain, United States Army, Recorder. The Assistant Secretary of War, President, National Board for Promotion of Rifle Practice. BULLETIN No. 25. WAR DEPARTMENT, WASHINGTON, July 31, 1919. The following instructions, previously published in certain War Department numbered circulars for the month of July, 1919, are published for the information and guidance of all concerned: Electric fans for posts, camps, and stations. Section. II I_Electric fans for posts, camps, and stations. (Cir. No. 351, W. D., 1919.)-Provided funds are available and that the purchase is a proper charge against the appropriation, requisitions for electric fans approved by a department, division or Coast Artillery district commander, or by a general officer in command of a station not under direct control of any of the above in matters of supply may be filled in the usual manner. Such requisitions must bear a certificate to the effect that electric current is available and the issue necessary, setting forth the reasons why the fans are required. Ordinarily fans will only be issued where the temperature remains high for a length of time sufficient to justify the expense. The issue will not exceed the rate of one 16-inch fan per room, and in addition, when rooms are in excess of 1,000 square feet in area, one per 1,000 square feet of floor space or major fraction thereof. A smaller fan, of about 12 inches in diameter, will be issued when rooms have less than 500 square feet of floor space. [412.44, A. G. O.] II__Computation of foreign service. (Cir. No. 352, W. D., 1919.)-In completing the War Department foreign service roster, beginning with January 1, 1917, and for future computa130680°-19 2 tions, service in the following-named places will be counted as foreign service: Alaska. Canal Zone. China. Hawaii. Mexico. (Punitive Expedition, 1916 and 1917). Philippine Islands. Service with Porto Rico Regiment of Infantry outside Service overseas with all American Expeditionary Service when attached to foreign armies in actual Foreign service will be counted from the date of departure from the continental limits of the United States of America to the date of return, both dates inclusive. All officers of the Army will be guided by the above in computing foreign service, but nothing in this circular will be construed as in any way modifying the foreign service roster in effect up to and including December 31, 1916. |