Accuracy. The gun world revolves around the word. Everyone wants an accurate gun, hunters in particular since an inaccurate one means no meat in the freezer. What is accuracy, though, and how much do you need in a hunting rifle?
Accuracy’s simple definition is hitting whatever you aim at. It’s not so simple in practice, however. What is an “accurate” rifle? Any good engineer will reply, “Well, it depends” when asked a technical question, and so it is with accuracy. A bench rest match shooter will define accuracy much different from someone who plinks at tin cans. It depends on your perspective. The match shooter will consider slashing his or her wrists if their rifle groups its shots wider than an inch or two at 1000 yards. The weekend plinker is happy if the cans in question just fall over at 20 yards, regardless where the bullet struck the can.
Accuracy’s close relative is precision. Most people confuse the two terms, but they are distinct. Accuracy is hitting an intended target. Precision is hitting it again and again in a predictable manner. Most shooters, hunters included, won’t settle for a mere hit, they want the confidence they can hit something with every shot. So, what are the factors which make up an accurate hunting rifle, and how much accuracy do hunters need?
1. The “Kill” Box
A kill box is a term used by military snipers. It is the area a bullet must hit to do sufficient damage to a target, an enemy in the sniper’s case. In short, it is the vital zone on any living target, human or animal. A hunter strives to place their bullets in a game animal’s upper thoracic cavity, its chest. A game animal’s chest contains the most vital organs to sustain its life: the heart and lungs. It is also the second largest area on a herbivore after the abdomen. While the brain is vital, too, it occupies an animal’s head, which is much smaller. The smaller a target, the more difficult it is to hit. Since a bullet through the heart or lungs will incapacitate and kill an animal in short order, and the chest cavity is a large target, most hunters aim for it rather than the head.
An animal’s vital zone varies with the animal’s size. For deer-sized game, the kill box is six to eight inches in diameter and depends on species and gender. A whitetail doe or a pronghorn’s is closer to six-inches, and a mule deer buck, eight. Large game, such as elk or moose, have a ten-inch, or so, vital zone.
2. A Thousand Kill Boxes
Now imagine a pipe, the vital zone’s diameter, which extends from your rifle’s muzzle to the target animal. You fire a bullet. It appears to rise when it leaves the barrel because the barrel is tilted a bit upward compared to your scope. This tilt is necessary to compensate for gravity. The moment the bullet leaves the barrel, gravity begins to pull it toward the Earth’s surface. Since the bullet does not have its own propulsion source like a rocket or an airplane, the air also acts upon it and it loses speed. This velocity loss is called drag. The drag and gravity combine to turn the bullet’s path from a straight line into an arc.
Back to the pipe. The bullet is fired, it rises relative to the sight line, loses speed due to drag and falls back toward Earth under gravity in an arc shaped path. At some point on its upward trajectory, it will touch the pipe’s top, and then it will fall until it hits the pipe’s bottom. The distance from the muzzle at which it hit bottom is called the Maximum Point Blank Range, or MPBR. It’s as if a thousand kill boxes were stacked together along the pipe’s length.
If your rifle is sighted correctly, your bullet will hit an animal in the vital zone if it stands anywhere along this pipe out to the MPBR. It’s a bit more complicated in real life, but this is the basic idea. For all the details on MPBR, see our article: The Max Point Blank Range Myth (Stuff You Need to Know).
3. Absolute Accuracy (The Almighty MOA)
In theory, as long as you hunted game no farther away than your particular rifle and load’s MPBR, you’d never have to worry about how accurate it is the word’s strict sense. Trouble is, critters are notorious for not fulfilling a hunter’s wishes. Here’s where you need to know how accurate your gun is and where you can expect your bullet to hit at a given range beyond the MPBR.
No gun ever fires every bullet to the exact same spot every time. There are just too many variables: production tolerances in the rifle and ammunition, atmospheric changes, up slope or down slope effects, and the shooter, to name a few.
These variables cause a bullet to strike in the general vicinity where it’s pointed, but seldom the exact same spot. If, for instance, you fire three rounds, they should form a rough cloverleaf-shaped group around your point of aim. The distance between the farthest bullet holes (points of impact, or POI) is the group’s size. For convenience, groups are measured in inches, not millimeters or centimeters. I’ll explain why in a moment, so don’t panic if you’re on the metric system.
If you drew a line from the muzzle to each bullet’s POI, it would form a cone. If you continued those lines from the POI out to infinity, you’d see the cone widens as the range from the barrel increases. It is inside this cone you can expect all further shots to hit, what I call the Cone of Probability, or CoP.
Back to the inches. A cone forms an angle, and this angle, measured in degrees, is predictable out to infinity. The CoP formed by rifle shots is so narrow it is more useful to measure it in minutes of angle. One Minute of Angle (MOA) is 1/60th of one degree. Turns out, one MOA is just a tick larger than one inch at one hundred yards. You metric buffs will just have to convert, sorry. For convenience, most shooters just round an MOA to an inch since the difference is immaterial until you get past a few miles.
A rifle which groups its shots into one inch at 100 yards is accurate to 1.0 MOA. You guessed it, this same gun will then shoot into two inches at 200 yards, three inches at 300 yards, and so on. A 2.0 MOA gun shoots into two inches at 100 yards, and you can do the math for the rest. This is why it is more convenient to use English measurements. The other measurement method is to use Milliradians, or “Mils,” which matches up with the metric system much easier. If you want to learn all about Milliradians, I suggest you research the subject on the internet or talk to a math teacher or military sniper instructor.
4. The Real (Hunting) World
Answer the following two questions and you can determine how accurate a hunting rifle you need . How big is the game you are hunting? How far away do you plan to shoot?
Let’s say you want to hunt whitetail bucks from a tree stand in Wisconsin. Wisconsin has thick, lush forests and you are lucky if you can see a deer more than fifty or sixty yards away in most places. A whitetail buck has a six to seven-inch diameter vital zone on average. You need, at an absolute minimum, a rifle which shoots no more than 12.0 MOA. Yes, you read it right, twelve! A 12.0 MOA rifle will put its shots into a six-inch circle at fifty yards (12 divided by 2), and nine-inches at 75 yards. All right, nine is bit on the large side for a whitetail buck’s vital zone, but as long as you keep your shots inside 60 yards, you’re fine. If you want some insurance, just in case you have a chance at a 100 yards shot, you need a 7.0 MOA gun. You don’t need a $3000.00, 0.5 MOA bench rest gun. Save your money and pick up a nice, used lever-action carbine in .30-30 Winchester, sight it for a 100 yard MPBR, and go hunt.
Now, if you are after elk in Colorado’s high country, things are a bit different. An elk has a ten-inch vital zone, in most cases, and you might have to shoot out to 400 or 500 yards across a creek drainage. How accurate a gun do you need? You’re right, 2.0 MOA (2.0 MOA at 500 yards equals a 10-inch CoP).
Pronghorn in Wyoming at 800 Yards? 1.0 MOA (8-inch CoP at 800 yards). Kudu on the Serengeti at 1000 yards? 1.0 MOA (10-inch CoP at 1000 yards). You get the idea.
Truth is, most game is shot inside 300 yards, with 200 the average. For most hunting, you need a gun with a 200 – 250 yard MPBR, so you won’t have to do any scope adjustment or hold over calculations when a shot presents itself. At these ranges, a rifle which shoots around 3.0 MOA is more than adequate for large game, and 2.0 MOA for medium game. If you hunt at longer ranges, a 1.0 MOA gun will do the job between 700 to 1000 yards, depending on the game size. This is a long way to shoot, and beyond most hunters’ skill level. So, if you’re an average hunter in average conditions after average game, don’t obsess over the latest mega-dollar precision rifle the gun industry’s marketing departments say you must have. Is more accuracy good? Without a doubt, and if you have more than you need, fine, just don’t over-think the problem, or over-spend to solve it.
Other helpful stories you’ll like:
LocaCarnivore Expert: Best Cartridge for Long-Range Elk [Virtual Test]
Long Range Hunting: Do it Right or Go Home
LocaCarnivore Expert: How Powerful a Hunting Rifle Do You Need?