bore sighting a scoped rifle before sighting in

[timmy]

This question comes up occasionally. There are a number of ways one might pre-adjust the telescopic or other optical sights on a weapon before going to the range, in order to conserve the amount of ammunition needed for the process. I recognize that there are many methods of doing this. The best one uses equipment for the task, but this may be too expensive for some (like me!). So, here's a description of how I do it. It may help you, or give you an idea about how another method will serve you better.

I have a >2 meter high wooden fence in my back yard. From my living room, it is about 10-15 meters to this fence, and there is a direct line of sight from the living room to the fence.

The first thing needed for my method is a distance with a direct line of sight to a specific point. Looking at the fence from my living room, there is a large wood knot in one of the boards that is easily visible though an optical sight.

I set up my Wife's ironing board in the living room and select some pillows to put on the ironing board. I push a crease in the pillows so that I can place the rifle in the crease in a way that it will stay put. This takes a bit of adjusting.

The rifle needs a clear bore for this process. For a bolt rifle, I remove the bolt. For my Ruger #1, I drop the breechblock. For my SKS and AK, I remove the action cover, bolt and carrier. The idea is to be able to see through the bore from the rear of the rifle.

Next, standing behind the rifle, I move it around until I can see the knot through the barrel. By moving the rifle on the pillows, I can get the rifle to stay put, so that I can see the knot hole through the bore without touching anything. Then, I look through the scope or optical sight to see if it is centered on the knot hole.

At about 10 meters, the bullet will be rising to the line of sight (remember, the scope is above the barrel's sight line), which is what you want. However, the exact distance here isn't critical.

By sighting through the barrel, you may feel that this isn't exact. However, sighting through the barrel is just like sighting though a peep sight, and relies on the eye's tendency to find the center of a hole instinctively.

This process takes a bit of fiddling around. Once you figure out how to set up your pillows in a way that allows the rifle to stay put without touching it, you are on your way. You will have to go back and forth between adjusting the scope and then realigning the bore to your point of aim several times, but after a bit, you'll only need a few such processes to get the scope pre-adjusted.

Put everything back together. Now, you have a choice to make: If you aren't confident in your adjustments, get a paper plate and staple it to a stick, and put a black circle with a felt tip pen on the plate. (You don't have to use a paper plate. Any piece of cardboard or stiff paper that's about 25 cm in diameter will work.)

If you are using the paper plate, when out at the range, pace off about 25 paces and put the stick in the ground. Go back and shoot the plate and note where the bullet strikes. At this range, the plate is about the same size as a target 4 times larger at 100 yards. So, if your shot is, say, 3 inches to the left, you will adjust your scope to move the point of impact 12 inches back to the right. The same principle applies to a shot that's too high or too low.

You shouldn't have any problem hitting a target after bore sighting by eye, if you've done it right, and one sighting shot should provide enough information for your next shot to print on paper at 100 yards. (I don't usually need to fire a shot at 25 yards with my method. However, one shot at 25 yards may save you several at 100 yards if you can't hit paper at the longer distance.)

Now, you should be able to hit paper at 100 yards, and you can adjust your scope accordingly. For most rifles, I usually use the old rule of sighting in at 3 inches high at 100 yards. But your rifle/cartridge/shooting situation may have different requirements.

After everything is adjusted, I prefer to shoot a 5 shot group to ensure everything is as it should be. Some people just use a 3 shot group for this.

Now you should be ready to go. If you have not used the rifle before, and especially you have a wood stock and there are varying weather conditions in your shooting area, you may wish to return to the range under different conditions (rainy, hot, cold, etc) and shoot another group to verify your adjustments. Some rifles are prone to wander when the weather changes the pressure the stock puts on the barrel/action.

[nagarifle]

nice one timmy, its good to see other ways of doing things.

glad you have understading wife, as mine would have few long shots to fire

[timmy]

I do have a number of faults that irritate my wife, but she's generally given me a lot of slack when it comes to guns. Even leaving them out, or failing to put up cleaning supplies promptly -- she understands guns and is very comfortable with them.

[Kittu]

hi timmy kindly can you explain whats are advantages of sighting a scope 3 inches above from centerpoint at 100 yards.i heard of shooters sighting 1.5 inches above as these will give them a blank range upto 300 yards.at what point should i sight my rifle at 100 yards iof make 30-06 rifle and 180 grains bullets to get a point blank range for a target of about 48 inches of size at 500 yards so that i dont have to adjust my scope for different targets at different range i will be vvery thankful as ammo quota is limited in india and very expensive too and for such experiment you need to have ammo in big qantity thanks

[TwoRivers]

Ashok: Before any one can calculate that for for you, the distance between then center axis of the telescope and bore must be known, as well as exact ballistics of the load in your rifle, and the ballistic coefficient of the bullet. There is no way to get a "point blank range" sighting for a .30-06, any load, any rifle, for 500 yards. No shoulder fired rifle, as far as that is concerned.

[dr.jayakumar]

thanks timmy,i just got my rifle tuned using your method.
regards

[nagarifle]

Ashok: Before any one can calculate that for for you, the distance between then center axis of the telescope and bore must be known, as well as exact ballistics of the load in your rifle, and the ballistic coefficient of the bullet. There is no way to get a "point blank range" sighting for a .30-06, any load, any rifle, for 500 yards. No shoulder fired rifle, as far as that is concerned.

and lets not forget the climatic changes and the wind factor which will also make a different

[Vikram]

Excellent post,Timmy.Learnt something that can be very useful.Thanks for sharing.


Best-
Vikram

[MoA]

hi timmy kindly can you explain whats are advantages of sighting a scope 3 inches above from centerpoint at 100 yards.i

generally there are several reasons you do this. A lot of people Including me like to have the impact higher than the POA, so that you can control a group by aiming at the same point, or adjusting for conditions based on you 1st shot PoA.

With a given load and cartridge having the POI higher at 100, will theoretically give you at PoA=POI at a given longer range. Without having to fiddle with the scope. A ballistic chart and a zero stop on your scope allows you to keep POI=PoA at any range theoretically. You also need to be able to read conditions, particularly wind and mirage. Elevation is a smaller issue. Of course everything is predicated on a consistent load.

[timmy]

Ashok: This is pretty much the common practice in the Western USA where I hunted. The 1.5 inch figure you mention is the commonly used distance between a rifle's bore and the line of sight from a telescopic sight (i.e., a "scope").

Here's the idea behind sighting in 3 inches high at 100 yards.

First of all, many ranges don't have a 200 yard course available. However, in this case, the method is tied into hunting. For most of our game in the Western USA, a heart-lung shot will be fatal if the bullet hits in an area of about 6 inches to 8 inches in diameter. This would be true for deer, elk (the American Elk, or wapiti) and other game animals.

When one sights in 3 inches high, aim can be taken directly with no hold over or under for quite some distance. For instance, I use a .270 and the ballistics for my .270 handloads using a 130 grain bullet at about 3150 fps mean that, when I am sighted in 3 inches high at 100 yards, my bullet trajectory will look something like this:

50 yards - 1.5 inches high
100 yards - 3 inches high
150 yards - 4 inches high
200 yards - 4 inches high
250 yards - 3 inches high
300 yards - 0
350 yards - 4 inches low
400 yards - 10 inches low
500 yards - 18 inches low

What this means is that I can shoot dead on to the point of aim of the crosshairs of the scope out to about 350 yards without holding over or under -- just shoot -- and if my aim is true, I will hit the vital heart-lung area of my quarry.

I used a 4x Leupold scope on that rifle at the time, and right now, I would not trust myself to shoot out to 350 yards without a great deal of practice. But back in those days, my eyes were good and I shot a lot at the range and in the field, so I felt that I could shoot out to a considerable distance in a sportsmanlike manner. In actual practice, the longest shot I took was at around 275 yards and I was successful.

Some rifle rounds (and when I say "rifle rounds," I am speaking of commonly used big game rounds in the Western USA, like .30-'06, .300 Magnum, 7mm Magnum, .270, and other such cartridges) will drop faster and may not reach out quite as far with a 3 inch high at 100 yard sighting in -- for instance, a 150 grain .30-'06 might drop outside of the 6 inch to 8 inch circle at a shorter distance than my .270, but it will still shoot out to a considerable distance without requiring any hold-over correction. It would certainly be workable for most hunting ranges.

A number of aids for figuring these sorts of things are available, although the chart I presented that I use for my rifle was one I obtained many years ago, so long that I don't remember where I got it from. But one very useful source of ballistic information is the Sierra Reloading Manual (Sierra is a maker of bullets used for reloading). They give pretty comprehensive ballistic tables for there products, and most such information is calculated from similar "model bullet" data. The main differences in shape that will affect these sorts of things commonly used in hunting cartridges (such as the ones I listed) would be the spitzer, or common pointed flat-based bullet, the boattail, which as a bevel of about 9° or so at the base, making it more aerodynamic than the flat-based spitzer (it cuts the air better and shoots flatter), and the round nose, less aerodynamic but often used for heavier bullets and for thick brush hunting. The round nose is the least aerodynamic of the three bullets I've mentioned.

Another type of bullet commonly encountered is the flat-nose, which is used in lever action guns with a tubular magazine, such as the Winchester 94 or Marlin 336. Using pointed bullets in a tubular magazine can cause a chain reaction: the point of one bullet sets off the primer of the round ahead of it when the gun recoils after firing. Flat-nose bullets aren't as aerodynamic as the spitzers and boattails.

There are also step-boattails, hollowpoints and other shapes, but this will help you get a feel for the basics I refer to in my post.

[nagarifle]

and the temp also plays a part, i remember being instructed that in cold climes ie -5c + shot will go low and the opposite in hot climes. or something like that