Spirit of '76
Boresighting a Scope

Introduction

These instructions assume that you have properly mounted the scope on your rifle. Once the scope is mounted, it is necessary to boresight the rifle, and finally, to finalize the "sighting in" procedure with one or more test shots. One thing to keep in mind is to use the rear ring for initial windage adjustments. Use it to get as close as possible, rather than "use up" scope clicks for this purpose.

There are a number of products available for boresighting a rifle. Some are optical, and some even use a small laser to accomplish this task. These devices are specialized tools for those who do A LOT of boresighting. While they are very accurate and easy to use, they also tend to be rather expensive.

Unfortunately, most of use can't really justify the expense of one of these products, as we only occaissionally mount a new scope on our rifles. Here are instructions for various methods of boresighting and final "sighting in" your rifle and scope without these specialized tools.

Initial Boresighting

Method 1 : NO SHOTS ARE TAKEN

This method can be used at either a public or private range. It can also be performed very easily ALONE. You should not need any assistance from anybody. It can only be easily used on rifles that allow an unobstructed view with your eye through the barrel. This will work for bolt actions, single shots, and lever actions (if you're willing to remove the lever/bolt at the range. It doesn't really work for autoloaders and pump actions.

• Remove the bolt, allowing a straight view through the barrel.
• Choose a target downrange.
• Place the rifle in a good, sturdy rest so that it cannot move, and align the rifle so that the target appears in the center of the bore.
• Without moving the rifle, use the scope ring adjustment to place the vertical part of the crosshair as close to the center of the target as possible.
• Use the windage knob of your scope for final fine adjustments.
• Use the elevation knob on your rifle to place the horizontal part of the crosshair on the center of the target.

Method 2 : NO SHOTS ARE TAKEN

YOU MUST REMOVE THE BOLT AND ALL AMMUNITION FROM THE AREA AND BE CERTAIN THAT NOBODY ELSE IS HANDLING A FIREARM BEFORE THE 'SPOTTER' CROSSES THE FIRING LINE AND HEADS DOWNRANGE!!!!

This method is very similar to Method 1, but should ONLY be used when you're alone, and is best done AWAY FROM the range (your backyard should be fine). Nobody else may handle a firearm while these procedures are being followed! Like Method 1, it can really only be used on rifles that allow an unobstructed view with your eye through the barrel. One other drawback, besides not doing this where anyone is shooting and being the only ones present, is that this method requires an assistant. This will work for bolt actions, single shots, and lever actions (if you're willing to remove the lever/bolt). It doesn't really work for autoloaders and pump actions.

• BANISH ALL AMMUNITION FROM THE AREA.
• REMOVE THE BOLT, allowing a straight view through the barrel.
• Have a friend stand downrange.
• Place the rifle in a good, sturdy rest so that it cannot move, and align the rifle so that your friend can look centered down the bore with one eye open, and the other closed. Make sure there's plenty of light so he/she is certain that he's looking down the center.
• Without moving the rifle, use the scope ring adjustment to place the vertical part of the crosshair as close to the center of the eye as possible.
• Use the windage knob of your scope for final fine adjustments.
• Use the elevation knob on your rifle to place the horizontal part of the crosshair on the open eye.
• Call your friend back.

Method 3

This method can be used at either a public or private range. It can be used on ANY type of rifle, as it does not depend on an unobstructed view through the barrel. This method relies on having a spotter along to tell you approximately where your shots hit, if your backstop is soft sand. If your backstop is moist or packed sand or dirt, you may be able to pull this off without a spotter.

• Choose a target on the backstop downrange.
• Place the rifle in a good, sturdy rest so that it cannot move, and align the rifle so that the target appears centered in the crosshairs.
• Without moving the rifle, take a shot at the target.
• re-align the rifle so that the target appears centered in the crosshairs.
• Without moving the rifle, use the scope ring adjustment to place the vertical part of the crosshair as close to the bullet impact point as possible.
• Use the windage knob of your scope for final fine adjustments.
• Use the elevation knob on your rifle to place the horizontal part of the crosshair on the bullet impact point.
• Take another shot at a different aimpoint on the backstop to confirm.

Final Adjustment

At this point, you should certainly be on the paper. Now the final "fine adjustments" can be made so that your rifle is properly sighted in. For this procedure, a WELL-DEFINED paper target with multiple aiming points should be used.

• Place the rifle in a good, sturdy rest so that it cannot move, and align the rifle so that the target appears centered in the crosshairs.
• Without moving the rifle, take one or more shots at the target.
• re-align the rifle so that the target appears centered in the crosshairs.
• Without moving the rifle, use the windage knob of your scope to align the vertical part of the crosshair on the center of the bullet impact point(s).
• Use the elevation knob on your rifle to place the horizontal part of the crosshair on the center of the bullet impact point(s).
• Take another shot at a different aimpoint on the target to confirm.

Long Range

I've been asked questions like, 'I have a Win Model 70 in .308 Winchester with a 22" barrel shooting a 150 grain bullet using 40.0 grains of W748. The load book says it will generate 2700 fps out of a 24" barrel. If I sight it in at 100 yards, how low will it hit at 400 yards?'

My first response has always been, 'There's NO SUBSTITUTE FOR ACTUALLY SHOOTING IT at the range in question - you really should shoot that load at that range if you REALLY want to know where it will hit.'

My follow-up response is that we all realize that some of us DO NOT have access to shooting ranges over 100 or 200 yards, so here's another method. Remember that it will NOT be as accurate as actually shooting at that range, for obvious reasons.

If there are no 400 / 500 / 600 yard ranges near you, you can make a reasonable calculation by:

1. Chronograph the load. Take the average of 5-10 readings.
2. Note the center point of impact of groups of 3 or 5 shots when shooting at 50 and 100 yards, and further if possible. I shoot at 50, 100, and 200 yards. The further apart the range of your shots are, and the more ranges you take data from, the better. Also - the TIGHTER your groups, the more valid your measurement will be.
3. Use a good ballistics software package to predict where it will hit at XXX yards by "fitting" the bullet's BC until the calculated trajectory matches the ACTUAL MEASURED IMPACT POINTS (trajectory) - "bring the data in line" to match the actual shots. I like PCB, JBM, and PointBlank (all listed in the above link) -- all are freeware or shareware.
4. THEN I consider the elevations from the computer-generated table to be the best I can do, and I go with it.

Again, there's NOTHING LIKE ACTUALLY SHOOTING IT at the range in question. If you're a hunter, you owe it to your quarry to make clean shots.

22 January 2000