How sweet it is to be able to put shot after shot into the bull, shoot those small groups we all admire so. How do we set up the sights on our rifle to make that happen, though? This discussion will consider some basics in accomplishing that, shooting your favorite load, at your favorite distance and target.
A quick review of what exactly happens when we fire that shot, and the relationship of the flight of the bullet to the line of the sights is in order, so that we are all using the same terms. Assume we are shooting a rifle that is already correctly sighted in. When we put the rifle to our shoulder and line up the sights on the target, we are looking along the line of sight. This line is perfectly straight, as only light can be, and runs from our eye through the rear sight, then the front sight, then to the spot on the target we want to hit. Unfortunately, this doesn't coincide with the flight of the bullet. Since the bore of the rifle is below the sights, the bullet starts out below the line of sight, crosses it traveling upward, stays above it for a time, then begins to fall downward, crossing the line of sight exactly at the target. Every shot we fire will travel this curving loop. The bullet will reach its maximum height above the line of sight at a little more than 50% of the distance to the target, and this point is called the Mid-Range Trajectory. Once the bullet travels past the target, it will be below the line of sight until it stops, for whatever reason.
The problem we have in sighting the rifle in, then, is to adjust the sights so that the bullet falls back to the line of sight at exactly the distance of the target. We must also adjust them so that the flight of the bullet is exactly lined up with the line of sight from side to side, of course. Adjusting the up and down flight of the bullet is called adjusting the elevation, that of adjusting the side to side flight is called adjusting the windage.
Before we get to the actual process of adjusting the sights to hit where you want, some decisions must be made. Where do you want it to hit, for instance? We all want that bullet to fly to the center of the target, but at what distance? Target shooting or hunting? Heavy load or light? What sight picture are you going to use, 6:00 o'clock hold or center hold? These decisions must be made by each individual shooter, based upon what he needs the gun to do, bark a squirrel, knock down a moose or punch holes in a paper target at close or long range. For some thoughts on these questions, see the FAQs Basic Ballistics and Practical Hunting Trajectories.
Throughout the process of sighting the rifle, it is wise to make changes in the sights only after having fired a number of shots, never a single one. While doing the fairly coarse, up close work, three shots are probably adequate, possibly even two. As the range increases, though, groups of 5 shots are recommended, especially if the changes to the sights involve any filing.
For this discussion, we'll assume you want the rifle sighted in to hit point of aim at 100 yards. We'll also assume you are sighting a new rifle, and have no idea what the sights are set for, if at all. You must figure a way to get started, to get "on the paper", as we say. You could just put up a big piece of paper at 100 yards, fire a few shots at it and hope the bullets hit the paper. If so, then the sights could be adjusted to bring the shots directly on the bull. That involves a lot of walking, though, and there is an easier way. Remember that we said the bullet crosses the line of sight the first time going upward? We'll use that fact to get you started. The point at which that first crossing takes place is, on average, somewhere in the 10-15 yard range in front of the muzzle. We'll split the difference, and place your target at 12 1/2 yards. Use a small bull or aiming point on a BIG piece of paper, and shoot from some kind of rest.
There is a paradox we must deal with at this point. In order to sight a rifle in properly, the rifle must shoot consistent, small groups. Yet, in order to develop an optimum load for the rifle, one which shoots consistent, small groups, it must be sighted in at least well enough to get on the paper. We compromise and do the best we can. Using manufacturer's recommendations, prior experience or advice from a knowledgeable friend, you must decide what initial load to shoot. Within reason, it really doesn't matter, but you must shoot that exact same load every time. If you shoot one load and then another, you will never make sense of the sighting-in procedure. The load can be modified later, honed to the best you can work out, after you have the rifle shooting on the paper at distance.
Fire a group at the big paper at 12 1/2 yards. Look at the center of the group and decide which direction it must move to put the group on the aiming point. Now adjust the sights to put the group where it should be in relation to the aiming point.
Sights come in two main categories, adjustable and fixed. Adjustable sights can be moved with impunity, because if you move them too far, you can simply move them back again, no sweat. Not so with fixed sights. Adjusting fixed sights for elevation involves filing away metal, which can't be put back, so you must be careful. I strongly recommend that throughout the sighting in process, you plan on making the bullets hit low on the target. The reason will become clear.
We'll consider the case for moving the bullet's point of impact (PI) in each of the four directions, right, left, up and down. Deciding which direction to move the sights to accomplish any one of these can be confusing. The general rule is: to move the point of impact by moving the rear sight, you must move the rear sight in the same direction you want the PI to move, while to do the same by moving the front sight, you must move the front sight in a direction opposite to the direction you want the PI to move. Rear = Same and Front = Opposite.
If the PI needs to move to the right, you must move the rear sight to the right, or the front sight to the left.
If the PI needs to move to the left, you must move the rear sight to the left, or the front sight to the right.
If the PI needs to move up, you must move the rear sight up, or the front sight down.
If the PI needs to move down, you must move the rear sight down, or the front sight up.
Because the effects of moving the rear and the front sights are opposite, it follows that while filing the front sight will raise the point of impact, filing the rear sight will lower the point of impact.
If the rifle has adjustable sights, the changes can be made simply by whipping out your handy screwdriver. If the sights are fixed, it's a little more complicated. Many fixed sights, both front and rear, are mounted to the barrel using dovetails, and the sight can be slid from side to side by lightly tapping them, using a hardwood dowel or a brass rod as a drift. In order to "move" the sights up or down, though, you must file metal from them. Any well made custom gun, and I presume most good production ones, come with the front sight too long, anticipating that it will be filed down in the sighting in process. Remember, metal cannot be replaced, so proceed with caution any time you are filing...go slowly, shoot, file, shoot. Too much filing may well mean the sight must be replaced.
Once the group is where you want it at 12 1/2 yards, you are ready to shoot at a greater distance. It may be that the bullets will land on the paper at 100 yards now, and you can move to that distance and make the final adjustments. If they aren't on the paper at 100 yards, then repeat the 12 1/2 yard exercise at 25 or 50 yards. Keep adjusting the point of impact at each greater range until bullets land on the paper at 100 yards, then do any final adjustments. Throughout all these maneuvers, keep the groups below the point of aim, as was mentioned before. This is because you must be very careful not to file too much metal off that front sight. Shooting low means the PI must be moved up. Moving the PI up by adjusting the front sight means moving the front sight down (front = opposite, correct?). The only way to move the front sight down is to file it so it is shorter. I make this the very last thing I do in sighting a rifle in. Once the windage is correct, and the group is falling below the point of aim, I slowly and carefully file down the front sight to bring the group up and directly onto the bull.
Now that the rifle is sighted in for 100 yards, it would be good if those fixed sights stay exactly where you have them. To guarantee that for windage, side to side, it is a good idea to "stake" or "peg" the sights in place. Take a small cold chisel and strike a light blow so as to cause a shallow cut or dent across the junction of sight and barrel at the dovetail. This will lock them in place, and will also give you a quick way to check if they have been knocked out of alignment.
Sighting in using this method is a fairly crude way to do it, but it works well. There is more to be learned, though, for those interested. With the rifle sighted in for 100 yards, and shooting nice tight groups with the best load you can develop, it's a good idea to go one step further. Since we know the bullet is flying in a looping curve, first up then down, it is obvious that the bullet will be above the line of sight for most of its flight to the target. How far above? An important question, if you want to get the most out of the rifle in a variety of situations. Important, but easy to answer. Back to the range. Simply shoot the best groups you can at 25, 50 and 75 yards, with the sights set where they are. See how far above the point of aim, or line of sight, the group is at each distance. Mark it down, remember it. It could help you win the prize and amaze your friends at a shoot, someday.
There is a more technical approach to the problem which some may be interested in. If a load can be chronographed and an exact velocity determined, and if a ballistics program is available, you can proceed in a different way to the same goal. With velocity known, a theoretical trajectory can be calculated and plotted. This will provide information as to the distance of the bullet from the line of sight, above or below, at any chosen distance. As an example, the chart in the Practical Hunting Trajectories FAQ showing the trajectory for a .530 ball at 1800 fps and sighted in for 100 yards, shows us that the bullet is above the line of sight by 0.96" at 25 yards, by 1.88" at 50 yards, and by 1.67" at 75 yards. Since the trajectory for any given bullet is exactly the same at any given velocity, you can use this information to simplify your sighting in procedure. You simply pick a distance and sight the rifle for the proper spot in relation to the line of sight. If you elect to use 50 yards, for instance, you carefully sight the rifle in to hit 1.88" high at 50 yards. All other points in the trajectory will fall in line, and the rifle will be properly sighted for 25, 75 and 100 yards, also. Because of the number of variables in black powder shooting, it is a wise shooter who actually fires at each distance, just to make certain there was no slip between the theoretical and the actual trajectory, under his conditions.
©1997 B. E. Spencer