I 



'Forest and Stream" Trajectory Test. 



{Continued from page 367.) 

 n^HE exact manner in -wliicli the tests were made, and tlie 

 subsequent calculations to get at tlie tables published 

 may be best and most clearly explained by taking the follow- 

 ing illustrations of one set of screens with the accompanying 

 target, and showing by them the method of working down 

 the results into their published form The Springfield rifle 

 may be taken since this shows bullet marks on the target 

 above and below the center line. First of all it should be 

 understood that the weapon was fitted to the rest and special 

 attention paid to having it level across the piece, that is, 

 having the sights in a vertical line above the center of the 

 bore. Then it was sighted on the target and a shot fired. 



The position of the hit was noted, the bullet hole stopped 

 with a patch and a second shot fired to get the arm bearing 

 well toward the bullseye. In the case of this particular 

 rifle the first trial shot struck rather high to the left, the 

 second was in good elevation, just to the left edge of the 

 bull. All was now ready for measurements, and a plug tit- 

 ting the bore was put in the muzzle, a pin in the center of 



this plug of course gave the center of the bore at the muzzle. 

 The distance in a plumb line from this pin to the lOO-yard 

 stake set by the surveyor was then taken by Mr. Sinclair 

 with a Brown & Sharpe improved vernier caliper having a 

 steel rod with points tempered and jaws ground, and capable 

 of measuring with unerring accuracy to the thousandth part 

 of an inch. This height was recorded in the note book. 



5- 



Upon a notched stick the same distance was given as close 

 as a carpenter generally measures, and with a spirit level 

 the carpenter assistant set out to set up the screens on 

 the 25, 50 and 75 yard posts respectively. Upon each of 

 the screens already stretched and dry was drawn with a 

 right-line pen a fine ink line at right angles to the frame. 

 This Hoe was set about the same level as the gun muz- 



zla, paying special attention to having the line level, by 

 using the spirit level. While this was going on, the work 

 of a few moments only, the arm was thoroughly scrubbed 

 out with a sharp brueh, but without removing it from the 

 rest, so that whatever of barrel buckling or "whipping- 

 down" of the muzzle which might have affected the trial 

 shots was not disturbed in making the final test shots. While 

 the screens were being adjusted, too, the notes were taken of 

 the weather conditions from the fine instruments sent us for 

 the test by Gall & Lembke, of this city. All was now ready 

 for the first shot. When it had been fired the hole or 

 puncture in each screen was marked No. 1, as was the bullet 

 hole in paper target. As the markers stepped aside a second 

 shot was fired, and this in turn was marked No. 3 on each 

 screen and on the target, and so on to the end, each shot 

 passing through the screens and target, until five had been 

 recorded. The screens had not been disturbed, neither had 



FOREST AND STREAM. 



the target paper. A slight lateral motion was given the 

 nfle m order to prevent the holes being too closely bunched 

 on the screens and on the target. This lateral shifting was 

 done m any. case where the shooting seemed to be too close, 

 and It maybe mentioned to the general credit of the rifles all 

 m the test that there were but one or two instances where it 

 was not necessary. 



With the firing of the last shot Mr. Sinclair took up his 

 gauge, and, putting in the plug, verified his muzzle meas- 

 urement; then on the first screen the distance from the sur- 

 veyor's stakG below to the fine ink hne was taken and re- 

 corded, at the same time an eye being directed to the 

 question of the correctness of the level set by the assistant. 

 The next screen and the next were similarly treated and 

 recorded, and at the target the distance from the stake to 

 the line across the center of the bullseye was taken and put 

 down at once in the notebook. In other words, we have 

 now got on record the distance of a certain fixed line on each 

 screen and on the target from a known level. This level 

 having been determined in the first place by Charles H. 

 Haswell and verified later in the trials by Surveyor Meserole. 

 The figures as they api)eared upon the notebook were: 



Height of center of bore at muzzle 16.442 in. 



Heigkt of line on 35-yard screen 16.304 in. 



Height of line on 60-yard screen. . . . ., 16.356 in. 



Height of line of 50-yard screen 16.256 in. 



Height of line on target 17.063 in. 



The screens were then cut from the frames, and after the 

 field work was over, they were tacked down on a smooth 

 table and the heights of the centers of the bullet holes taken 

 in a line at right angles with the line on screen. Let us fol- 

 low shot No. 1— on screen at 35 yards it stood 3.356 inches 

 above line; on screen at 50 yards it measured 4.576 inches 

 above line; on the 75-yard screen it measured 5. 163 inches, 

 while on the target it struck 3.693 inches above the center 

 line. Now with these figures it will at once be seen that 

 every element and factor necessaiy to the determination of 

 the trajectory curve is present. The proper way is to start 

 at zero at the muzzle, and with a corresponding zero at the 

 target get a line connecting them and then find the heights 

 of the bullet holes in the screens above that line. So far 

 as the screens are concerned, by adding together the height 

 of the line and the height of the bullet hole above the line, 

 we get the distance of the hole above the surveyor's level 

 line, and by subtracting the muzzle height we get the dis- 

 tance of the bullet hole above the muzzle. 



This calculation would take this form: 

 25 Yards. 



Height of screen line. . .16.304 in. 

 Height of bullet hole. . . 3.356 in. 



75 Yards 

 16.356 in. 



50 Yards. 

 16.3.56 in. 



4.576 in. 5.163 In. 



30.938 m. 

 16.442 in. 



31.418 in. 

 16.443 in. 



]'.».560 in. 



Muzzle height 16.443 in. 



BuUet hole above muzzle 3.118 in. 4.490 in. 4.976 in. 



Now these would be the trajectory heights if the zero 

 point at target, that is the point where the bullet struck, 

 corresponded exactly with the zero point at the muzzle, 

 that is the height of the muzzle, but the bullet struck 

 2.693 inches above the line on the target, which, as 

 we have seen, stood at 17.062 inches above the base 

 line. The calculation now is to find the difference in 

 height between the point where the bullet started and the 

 point where it struck, and the figures stand : 



Line on target 17.063 in. 



Bullet hole above line 3.693 in. 



19.754 in. 



Muzzle height 16. 443 in. 



Bullet above muzzle 3.3J3in. 



The problem now is to distribute this 3.312 inches of 

 height along the screens. It is manifest that the figures we 

 have found from the screens are deceptively high. We need 

 a new base line, from the muzzle to the hole on target, and 

 not from the muzzle to the center line of target. This is 

 shown on Fig. 1. 



Pi' 



M is the muzzle. C same level on target. B the point 

 struck. C B is the 3.313 inches we have determined. A 

 simple geometrical problem tells us that at A, where the 35- 

 yard screen is, the height A F will be one-quarter of the 

 height C B. At D, where the 50-yard screen is located, the 

 height D H is half of the height C B, and at E, where 

 the 75 yard screen is located, E K is three-quarters of C B. 

 In actual numbers the record stands: 



CB =3.313 in. 

 A F=3^ of C B=0.838 in. 

 DH=>^of CB=1.&56 in. 

 E K=% of C B=3.484 in. 

 Going back to our first table, we are now able to complete 

 it, as follows: 



25 Yards. 



Height of screen line 16.304 in. 



Height of bullet hole 3.356 in. 



50 Yards. 

 16. 356 in. 

 4.576 in. 



75 Yards. 

 16.2.56 ini 

 .5.162 in. 



This then is the record of one round through the three 

 screens, and we hope we have made it plain enough to be 

 understood by any one. 



Shot No. 3, it wiU be seen, struck the target about the 

 center hne, and without doing more than giving the figures 

 the calculation blank shows, as follows, the screen lines and 

 muzzle height and target line remaining as before: At 35 

 yards the bullet went 3.586 inches above screen line, at 50 

 yards it was 3.312 inches, and at 75 yards it stood at 3 115; 

 while on the target it struck-. 008 above the center line in- 

 scribed there, which, it will be recalled, stood 17.063 inches 

 above surveyor's line. The calculations then stand : 



Height of screen line. . . 

 Height of bullet hole . . . 



25 Yards. 

 ....16.304 m. 

 .... 3.586 in. 



50 Yards. 

 16.356 in. 

 3.315 in. 



75 Yards. 

 16.356 in. 

 3.115 in. 



18-890 in. 19.671m. 19.371 in. 

 Muzzle height 16.443 m. 16. 443 in. 16.443 in. 





19 560 in. 



20.932 in. 



21.418 m. 





..16. 443 in. 



16.442 in. 



16.443 in. 



Bullet hole above muzzle. 



.. 3.118 in. 



4.490 in. 



4 976 in. 



Target correction 



—0.828 in. 



1.656 in. 



2.484 in. 



True trajectory 



. 8.390 in. 



3.834 in. 



2.492 in. 



2.448 in. 



Target correction —0.1.57 in. 



3.839 in. 

 0.314 in. 



8.929 in. 

 0.471 in. 



True trajectory 3.391 in. 3.915 in. 2.4.58 in. 



In shot No. 3 we find the screen heights to be at 25 yards, 

 3.103 inches; at 50 yards, 3.334 inches; at 75 yards it wa.s 

 1.453 inches, and at the target it struck 3.348 inches Mow 

 the center line. This last will necessitate a reversal of our 

 geometrical diagram, as follows: 



The lettering is the same and the same principle applies, 

 but the line of heights first obtained on the screens are 

 plainly too low and need to be increa.sed as the bullet hole is 

 brought from its actual position below the muzzle to a point 

 above it, and the table stands: 





25 Yards. 



50 Yards. 



75 Yards. 



Height of screen line. 



..16. 304 in. 



16.3.56 in. 



16. 356 in. 



Height of bullet hole. 



. 3.103 in. 



8.834 in. 



1.453 in. 





18.407 in. 



18..580 in. 



17.709 in. 





.16.443 in. 



16.448 in. 



16.442 in. 





1.965 m. 



2.138 in. 



1.367 in. 



Target correction 



4-0.407 in. 



0.814 in. 



1.231 in. 





2.373 in. 



3.953 in. 



2.488 in. 



, Shot No. 4, when examined on the screens and target, 

 was found lo show heights as follows above the ink lines : 

 25-yard screen, 2.753 inches; 50-yard screen, 3.556 inches; 

 75-yard screen, 3.465 inches, and target, 0.556 inches. In 

 this case the bullet, striking above the muzzle height, there 

 would be a correction to be made by subtraction, the figur- 

 ing standing : 



25 Yards. 



Height of screen line. , .16.304 in. 

 Height of bullet hole. . . 2.7.53 in. 



19.057 in. 

 .16.442 m. 



Muzzle height... 



3.615 in. 



Target correction — 0.394 in. 



50 Yards. 

 16.a56 in. 

 3.556 in. 



19.918 in. 

 16.448 in. 



3.470 in. 

 0.588 m. 



75 Yards. 

 16.356 in. 

 8.465 in. 



True trajectory 3.831 m. 8.883 in. 8.,S97 in. 



The fifth and last round, it will be seen by the target dia- 

 grams, strikes below the center line, and in this respect 

 resembles No. 3; and a similar mode of reaching the result 

 is followed. The screen and target measurements were : 

 25-yard screen, 3.406 inches; 50-yard screen, 3.804 inches; 

 75-yard screen, 3.366 inches; and on the target 0.960 inch 

 below, and the calculation stands: 



85 Yards. 



50 Yards. 



75 Yards. 



.16.304 m. 



16.356 in. 



16.356 m. 



. 2.406 in. 



8.804 in. 



3.866 in. 



18.710 m. 



19.160 in. 



18.682 m. 



16.443 m. 



16.443 in. 



16.442 in. 



3.368 in. 



2.718 in. 



3.180 in. 



-f0.085 in. 



0.170 in. 



0.8.55 in. 



3.3.53 in. 



3.888 m. 



3.435 in. 



Round. Muzzle. 25 Yards. 



1 3.390 in. 



2 3.291 in. 



3 3.372 m. 



4 2.331m. 



5 2.353 in. 



All that now remains is to join these shots into a table to 

 get the average for the five shots; and, to make it more 

 complete, we insert what is omitted, as understood, in the 

 report on each arm, the zero point which we have found for 

 muzzle and target: 



50 Yards. 75 Yards. Target. 



3.834 in. 2.493 in 



3.915 in. 2.458 in 



3.953 m. 3.488 m 



8.883 m. 3.397 in 



3.888 in. 3.4^5 in 



Average 2.325 in. 2.894 in. 3.454 in. 



The nomenclature of the wind seems to be, judging from 

 letters of inquiry received, not clearly understood by all of 

 our readers; and when we speak of a "10 o'clock" or a "6 

 o'clock" wind, the terms convey to the mind of some of our 

 readers an impression of the actual direction in which the 

 wind was blowing. It would be plainly out of the question 

 to use the points of the compass in describing the direction 

 of the wind, unless we had for constant reference a map of 

 the range. In fact the firing during the tests was almost 



