12/10/2012 So you want to be a long-range hunter? You have a super-accurate rifle and you have tuned the ammo until it punches little bug holes in the target instead of groups. The trigger is crisp and clean and you have the best optics money can buy on top of the gun. So, what’s next? Lots and lots of practice, for one thing. The Laws of Gravity It might seem obvious, but long-range shooting is about variations in distance. If our bullets simply flew straight to the target it would be pretty easy, but they don’t. Bullets, like everything else on the planet, are subject to the laws of gravity. As soon as a bullet is free from the support of the rifle it starts falling to the ground at a rate of acceleration of 32.2 fps—per second. So after a bullet has been in flight for one second it is dropping to the earth at 32.2 fps. After two seconds it is dropping at a velocity of 64.4 fps and so on. The longer the shot, the longer the bullet is in flight and the faster it is dropping. While the line of sight is linear because gravity has no effect on it, the bullet’s flight is not. If your line of sight was exactly parallel with the bore of the rifle, the bullet would always impact below the line of sight as it exits the barrel below the scope. The greater the distance to the target, the farther below the line of sight the impact will occur. For example, a 180-grain bullet from a .300 Winchester Magnum impacts 63.11 inches low at 500 yards, but at 100 yards it’s only 3 inches below the line of sight. So we adjust the relationship between the line of sight and the bullet’s flight. To work correctly, rifles do not have the line of sight and the bore parallel. The bore of the rifle will actually be tilted up at the muzzle when compared to the line of sight. The bullet exits the muzzle about 1.5 inches below the line of sight for most scoped hunting rifles. Because the bore is tilted slightly relative to the straight line of sight, the bullet’s path will arc up through the line of sight. With our .300 Win. Mag. and a 200-yard zero, the bullet crosses for the first time at 20.5 yards. Even though the bullet is dropping toward the earth, its path will continue to rise relative to the line of sight until it reaches its peak. That varies with cartridges, bullets, velocity, zero range and other factors, but for our .300 Mag. with a 200-yard zero it happens at about 110 yards, where the bullet will be 1.86 inches above the line of sight. After that point the bullet will be moving closer to the line of sight until it crosses it again at 200 yards. From that point on the bullet will always be below the line of sight and the distance between the bullet path and the line of sight will grow exponentially larger as the distance increases. So what does that mean hunters? Well, first off, with most modern, high-velocity, bottleneck rifle cartridges you can pretty much ignore all this out to 250 yards or so. With a 200-yard zero the .300 Winchester’s bullet will be about 3 inches below the line of sight at 250 yards. So from zero to 250 yards the bullet is never more than 1.86 inches above or 3 inches below the line of sight. On big game this means you can hold on the center of the chest and you will hit the kill zone if you do your job. Even at 300 yards the bullet is only 7.3 inches below the line of sight. If you hold slightly high, but still on the critter—on hair not air—you will hit vitals. But after that things rapidly start to change. The .300 Win. bullet has been in the air for more than a third of a second and it is beginning to pick up drop speed. At 350 yards it is almost 13 inches below the line of sight. At 400 yards the bullet impacts more than 20 inches below the line of sight. At 500 that has doubled to 40 inches. It’s almost 70 inches at 600 yards. By 1,000 yards the bullet will impact almost 290 inches below the point of aim—that’s more than 24 feet. But if you move your zero distance out, you run into other problems. Suppose you zero that same .300 Win. Mag. for 400 yards: At 200 yards your bullet will be 10.2 inches above the line of sight. If you aim at a deer standing 200 yards away, you will shoot over his back. Remember too, this is with a .300 Win. Mag., one of the flattest-shooting cartridges. With many less powerful cartridges these numbers grow bigger due to slower bullet velocity. Considering that a lot more deer are shot at less than 200 yards than are shot past 200 yards, a 400-yard zero would be a mistake. The key to long-range hunting is to zero for a reasonable distance, like 200 yards, and then deal with the hold-overs for longer stuff. There are basically three techniques. Hold-Overs A smart hunter has a method. Now that we have laser rangefinders it’s easy to know the exact distance. If you know the hold-over for each distance and have something of a known size to use for a guideline, you can adjust. For example, if you are hunting northern whitetails and you know that the average mature buck measures 18-20 inches through the chest you can gauge how high to hold. Say the buck is at 400 yards: We know the .300 Win. Mag. drops 20 inches at that distance. So you would hold one deer thickness above where you want to hit, which is the center of the buck’s chest. That means you hold half a deer above his back. If the deer is at 500 yards there is a 40-inch drop, so you would need to hold two deer above where you want to hit, or one and a half deer above his back (I discourage trying it). A pronghorn measures about 15 inches through the chest, an elk about 25 inches: adjust accordingly. It’s not perfect, but it can work if you keep your cool and do the math. Clearly this is full of variables and there are too many things that can go wrong to consider it a precise technique for hunting. Say you are at 440 yards where the drop is 27.12 inches: Can you do the math in your head quickly? What if the deer is a runt and its chest measures only 15 inches, but you think it is 20? Are you sure you are holding two deer above your expected point of impact, not 2.3 deer or 1.7 deer? There are better ways. Dial-Ups Suppose your rangefinder says the distance is 400 yards again. Our ever popular .300 Win. Mag. will impact 20 inches low, and your scope has quarter-minute clicks. That means you move it four clicks to adjust for one minute of angle (MOA), which for all practical purposes is 1 inch at 100 yards. (It’s actually 1.047 inches, but let’s not split hairs.) At 400 yards one click will equal 1 inch, as an MOA at 400 yards is 4 inches. So, you adjust the scope up 20 clicks and aim at where you want to hit the deer. If he is at 440 yards, you come up 27 clicks. Simple, right? In theory, yes, but there are problems. The biggest problem is that a lot of scopes don’t work all that well. Often their adjustments are erratic, so they do not move the amount you expect. You think you dialed in 20 inches, but the scope moved only 16 inches, or maybe 27. I have seen this time and time again with scopes when trying to zero them. Or maybe it didn’t move at all because it’s stuck. (That happens a lot, too. That’s why you see savvy shooters tapping the adjustments on their scopes after moving them.) So, the shot is low but the recoil jars the mechanism loose. Thinking you didn’t go enough, you dial in another 20 clicks and the bullet sails over the buck’s back. This is particularly true with inexpensive scopes, but I have seen this with top-of-the-line brands as well.
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