3 The measurement of the mean radius was taken only in order that a comparison might be made with ammunition tested in previous years. The board is of the opinion, as expressed below, that the best indication of the accuracy of ammunition can be obtained by taking a mean of the mean vertical deviation and the extreme vertical deviation, this mean to be known as the "vertical error." The group measurement-that is, the measurement from center to center of the shot holes of the group that are farthest apart—was taken for the information of large numbers of riflemen throughout the country who are accustomed to measuring and judging accuracy tests in this manner. The first test, on the afternoon of July 1, 1919, was fired with pistol ball cartridges, caliber .45, model of 1911. This ammunition had been manufactured at Frankford Arsenal, being lots of regular manufacture selected for its accuracy. The conditions of the national pistol match in which this ammunition is to be used prescribe firing only at 25 yards. The board, therefore, decided to test this ammunition at this range, but also to test each lot at 50 yards, in order that it might be possible to compare this ammunition with that manufactured for this purpose in previous years and tested at 50 yards. Only one-half the number of groups were fired at 50 yards that were fired at 25 yards. Four special pistols in machine rests were used. These pistols consisted in automatic pistol barrels mounted in model of 1903 rifle receivers, and with rifle bolts so arranged that they could be secured in the rifle type of machine rest. Only two of these pistols were fired at one time on account of the limited number of machine rests available. Each pair of pistols were fired five groups of 10 shots each with one lot of ammunition, lots being changed when pairs of pistols were changed. With the first pair of pistols a 50-yard target was placed behind the 25-yard target on the right, and with the second pair behind the target on the left, and so on. In the tabulation of groups fired, given below, the reference numbers refer to groups fired at both 25 and 50 yards, the 25-yard target acting as a screen. Thus the two records identified by reference No. 1 in the tabulation below indicate one firing of 10 consecutive shots fired through a target at 25 yards on to a similar target at 50 yards. With each pair of pistols the groups were fired by command, and the 10 shots fired as rapidly as possible, in order that each of the pair of pistols should deliver its series of shots under identical wind conditions. Weather conditions were excellent, practically no wind existing. |