This table is only inserted because the figures contained in it have hitherto formed the bases of public knowledge and calculation; it is corrected and superseded by another on page [44]. Its errors consist in no deduction for the natural spread of the pattern and in the multiple adopted being based on the striking velocity of the first five per cent. of pellets.
He did this to discover the longitudinal spread of the shot pellets at various distances. If ever the chronograph could be used for taking differing shot velocities, this appears to be the way. But it has never been repeated, and some results appear to throw doubt upon their own accuracy. The various lengths of the shot spread on the targets moving at 200 f.s., at right angles with the line of fire, were as follows upon the top lines. On the bottom lines in the table the shot pattern spread, caused by the 200 feet per second, is multiplied by the ratio of greater speed of shot than the 200 foot-seconds of the revolving target. So that in the following table the bottom lines, in respect of each gun, represent something near the true length of shot column at each distance. The speeds taken in the foregoing table can be gathered from the Griffith figures on the next page. But if, for the 30 yards range, the truer mean speed of the shot column is wanted, this is equal to the striking velocity of the most forward pellets and the velocity of the rear of the column added together, and divided by two. For this calculation there is a slight inaccuracy originating in the following tables, because the striking velocity of the rear pellets has been taken at the full range, instead of at the length of the shot column less than the full range. This position can only be found by trial and error. It will vary the results by a yard or two. Inches have been disregarded in the tables.
It is often said that we want guns to send their shot up all together, but if we had so to time our “letting off” as to cause the game to fly on to a knife edge, with the shot spread out like a tea-tray, it is doubtful whether we should hit oftener than with a rifle. Lord Wolseley tells of seeing an officer who by means of a soldier’s rifle killed a wild goose flying high overhead.
Keeping the line of flight for such a shot would not be difficult, but the timing and allowance in front could not often be so cleverly arranged. That is the reason why there is a good deal of doubt whether we want to decrease the length of shot columns, and besides, if we did wish it, probably it could not be done. It is observable that the extra half-dram measure of powder materially increased the choke bore’s lengths of shot columns. It also had a very great influence in the increase of velocity at all distances.
The length of the column of shot from the cylinder gun is longer than the spread from the choke bore, and the longer the range the longer is the column; but strangely, at long range, according to these trials, one striking velocity of the first pellets in the load was exactly the same as that of the last pellets to strike the revolving target, although mean velocities for the range were very different. This almost shakes confidence in this chronographic record, but as the penetration tests always show more variation between pellets than the differences in any of these revolving target and chronographic records, it may be that the apparent paradox of pellets getting farther behind but nevertheless maintaining the same speed as those in front can be explained by a constant change of leaders, and if so, also of followers necessarily.
These phenomena do not occur except at the extreme distance of 55 yards, and they are totally absent even at that distance with the choke bore and 49 grains charge. It seems therefore only to be possible when the pellets have dropped to a low velocity. At shorter ranges there is sometimes an impact difference of 200 feet a second between the pellets of the same load. So that it is material to know the force of the whole charge, and the time up the range of the leading pellets is no guide, as differences equal to 320 f.s. have occurred in one load.
| Striking Velocity at Various Ranges in Foot-Seconds | |||||||
|---|---|---|---|---|---|---|---|
| on Mr. Griffith’s authority | |||||||
| By the fastest 5 p.c. of pellets. | By the next 25 p.c. of pellets. | By 45 p.c. of pellets. | By the mean of the bulk. | By the last 3 p.c. of pellets. | |||
| 15 yards | choke | (42) | 1013 | 987 | 974 | 952 | 813 |
| choke | (49) | 1050 | 1013 | 1042 | 965 | 798 | |
| cylinder | (42) | 1003 | 955 | 962 | 923 | 742 | |
| 25 yards | choke | (42) | 825 | 792 | 779 | 748 | 684 |
| choke | (49) | 890 | 840 | 806 | 809 | 699 | |
| cylinder | (42) | 810 | 769 | 750 | 724 | 615 | |
| 35 yards | choke | (42) | 691 | 661 | 660 | 632 | 523 |
| choke | (49) | 737 | 699 | 699 | 672 | 564 | |
| cylinder | (42) | 672 | 632 | 636 | 619 | 504 | |
| 45 yards | choke | (42) | 581 | 560 | 549 | 536 | 489 |
| choke | (49) | 633 | 598 | 592 | 573 | 527 | |
| cylinder | (42) | 561 | 538 | 523 | 494 | 488 | |
| 55 yards | choke | (42) | 377 | 365 | 362 | 344 | 342 |
| choke | (49) | 478 | 462 | 457 | 427 | 418 | |
| cylinder | (42) | 382 | 374 | 378 | 370 | 382 | |
As these are the only chronographic tests of shot pellets ever made with a view of finding out what really takes place, the striking velocities of the various proportions of the load at different distances are given here. But although this represents the only use of the instrument for this purpose, on truly scientific principles, ever recorded in print, the author would be sorry to affirm the absolute accuracy of the instrument on this or any other occasion, although the relative accuracy of one record to the other is much more likely to be correct.
The (42) and (49), after the description of the gun in the table on p. [41] refers to the load of Schultze powder, and in all cases 1⅛ oz. of shot No. 6 was used.
In order to arrive at striking velocity from these trials, it was necessary to compare the time taken at one range with that taken at another range by a different cartridge.