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Oh, what thoughts cross my mind...
Jan. 24th, 2010 11:03 amJack Reacher (the hero of a series of books by Lee Child) is an expert rifle marksman, but something Child has Reacher do in one of his adventures raised my eyebrows.
You see, back when we spent two marvelous weeks at Parris Island learning the basic craft of aiming and firing an M-14 to hit targets up to four football fields distant, one of the basic skills we were taught involved "dialing in" elevation and windage in order to adjust the weapon's rear sight. The reason for the adjustment has to do with two things: the force of gravity and the force of any wind that may be blowing.
You see, as the distance to the target increases, the further a bullet will fall as it flies toward the target. (The fact that it's moving horizontally doesn't change a thing. If you were to fire one bullet perfectly horizontally and drop another bullet from the same height at the same moment, then assuming a flat terrain, both bullets will strike the ground at the same time.) Therefore, as the distance to the target increases, the rear sight must be raised (the elevation setting) so that upon aligning the front and rear sights, the angle at which the barrel tilts up is increased, causing the bullet to fly along a parabolic path, above the line-of-sight, intersecting the target at the same elevation as the front sight.
The same basic principle applies to windage, where the barrel is tilted to fire to the left or right of the aiming point (depending on where the wind is coming from, and how strongly), so that by the time the bullet reaches the target, the wind has pushed the bullet back to the aiming point.
All during basic marksmanship training, the idea was to adjust the sights in such a way that you were always aligning the sights on the target. In the Child book, though, at one point, Reacher aims a sniper's rifle at his target by placing the scope cross-hairs somewhere else in his "sight picture."
And that's what's bothering me - or did bother me, because thinking the matter through with my fingertips like this has sorted things out for me. (That, and the realization that getting worked up over what potentially may be an error in a fiction story is probably not the best use of my time.)
What bothered me was the idea of "that's not how it's done" (and I'm convinced that, ceteris paribus, it isn't, and though I shot "expert" in boot camp, I'm no sniper). On the other hand, given everything else that was happening in the story, maybe Reacher's use of "Kentucky style" windage and elevation was an acceptable "field expedient."
Whew! I'm glad I got that out of my system! (As penance, I think I'll go reread Kipling's poem In the Neolithic Age.)
Cheers...
You see, back when we spent two marvelous weeks at Parris Island learning the basic craft of aiming and firing an M-14 to hit targets up to four football fields distant, one of the basic skills we were taught involved "dialing in" elevation and windage in order to adjust the weapon's rear sight. The reason for the adjustment has to do with two things: the force of gravity and the force of any wind that may be blowing.
You see, as the distance to the target increases, the further a bullet will fall as it flies toward the target. (The fact that it's moving horizontally doesn't change a thing. If you were to fire one bullet perfectly horizontally and drop another bullet from the same height at the same moment, then assuming a flat terrain, both bullets will strike the ground at the same time.) Therefore, as the distance to the target increases, the rear sight must be raised (the elevation setting) so that upon aligning the front and rear sights, the angle at which the barrel tilts up is increased, causing the bullet to fly along a parabolic path, above the line-of-sight, intersecting the target at the same elevation as the front sight.
The same basic principle applies to windage, where the barrel is tilted to fire to the left or right of the aiming point (depending on where the wind is coming from, and how strongly), so that by the time the bullet reaches the target, the wind has pushed the bullet back to the aiming point.
All during basic marksmanship training, the idea was to adjust the sights in such a way that you were always aligning the sights on the target. In the Child book, though, at one point, Reacher aims a sniper's rifle at his target by placing the scope cross-hairs somewhere else in his "sight picture."
And that's what's bothering me - or did bother me, because thinking the matter through with my fingertips like this has sorted things out for me. (That, and the realization that getting worked up over what potentially may be an error in a fiction story is probably not the best use of my time.)
What bothered me was the idea of "that's not how it's done" (and I'm convinced that, ceteris paribus, it isn't, and though I shot "expert" in boot camp, I'm no sniper). On the other hand, given everything else that was happening in the story, maybe Reacher's use of "Kentucky style" windage and elevation was an acceptable "field expedient."
Whew! I'm glad I got that out of my system! (As penance, I think I'll go reread Kipling's poem In the Neolithic Age.)
Cheers...
