Rifle Scope Mounting/Sighting Tips

The Importance of Good Mounting One of the most important contributing factors to the accuracy of your scope and rifle is the selection of the mount and care with which mounting is done. You cannot get by satisfactorily using a cheap mount. The slightly higher cost for dependable mounts that attach your scope solidly to the rifle will reward you handsomely over the years with dependability and consistent accuracy. Most modern firearms are drilled and tapped at the factory to receive scope mounts. If your firearms is not drilled and tapped from the factory, you should take it to a qualified gunsmith. If you have any questions about how to mount your scope, it is recommended that you take your firearms and scope to a qualified gunsmith. Note: Always check and verify that your firearm is unloaded. Attach the base: Place the unloaded firearm securely in a padded vice or a gun maintenance bench. Remove the filler screws in the receiver and clean the receiver surfaces to remove dirt and oil. Especially clean grease and oil from the screw holes. This prevents the base screws from loosening under repeated recoil. Carefully position and attach the base mount on the firearm using the provided screws. The windage adjustment screws go to the rear of the receiver and the dovetail insert goes to the front of the receiver. Tighten the screws as tightly as possible. Be firm when tightening because a slightly loose base is a common cause of inaccuracy and a shifting point of impact. However, excessive pressure can strip or snap the screw heads. Attach the ring: Do not use the scope as a lever when installing the scope in dovetail type mounts for the first time. The initial resistance to turning could warp the scope tube. Instead, use a 1" wooden dowel or metal cylinder to seat the rings. Attach the scope: Leave at least 1/8" of clearance between the edges of the ring and protruding surfaces such as turret housing, power ring and the flare of the objective bell. Before you tighten the rings, you should position the scope for proper eye relief. Loosen the ring screws so that the scope will slide easily. With the rifle at your shoulder and looking through the scope in your normal shooting position, slide the scope forward or rearward until the full field of view can be seen through the scope. You will notice an area of approximately 1/2" of eye freedom where the full field is visible. Move the scope to the forward most position for maximum eye relief. When the scope is properly positioned axially, rotate the tube until the horizontal crosswire is parallel with the ground plane. Tighten the ring screws as tightly as possible. Be firm when tightening because a slightly loose base is a common cause of inaccuracy and a shifting point of impact. However, excessive pressure can strip or snap the screw heads. Do not use adhesives on the ring screws. Note: If the distance between your eye and the scope is too close, you can be injured when recoiled. Make sure to have maximum eye relief. Eye relief on the most of pistol scopes is none-critical. Set the scope for full field of view when the pistol is held at normal arms length. Pre-sighting You will save a significant amount of expense and frustration by pre-sighting the scope to the rifle before you take it out for zeroing. Collimating, the most accurate and simple technique for pre-sighting, is the system most often used by gunsmiths. It can be done quickly in the shop before leaving for the range. If a collimator is not available, you can still do a good job of pre-sighting by a method known as " bore-sighting". At the range, set the scoped rifle up on sandbags or other steady rest and place a target at 100 yards. With the bolt removed, look through the chamber and move around the bore until you can see the bulls eye centered in the bore. Without moving the rifle from this position, glance through the scope and note where the reticle is positioned on the target. If the scope reticle is not closely aligned to target center, you need to adjust the base mounting screws. Do not use the scope windage and elevation adjustments for these pre-sighting adjustments or you will run out of adjustment for final zeroing. All ABO (USA) serviced scopes are tested to be certain that they provide maximum internal adjustment range. After testing, the reticle is centered in the scope optically and mechanically. However, variations in rifle receiver dimension, mounting holes drilled out of alignment with the receiver or barrels threaded into the receiver at an angle will cause initial scope misalignment. Therefore, it is important to make all major bore sighting adjustments using the mount adjustment screws. Make only final adjustments using the scope's internal windage and elevation screws. This will prevent running out of internal adjustments. Note: There is no acceptable way to increase elevation adjustments except to shim. Shim stock .010" thick, placed under the rear of the mount base will raise the point of impact about 7". To lower the point of impact, place the shim stock under the front end of the base. Zeroing a scope The range at which a scope should be zeroed is a matter of personal judgment. If you anticipate using the scope at distances of 100 yards or less, naturally a 100 yard zero is appropriate. Mid-range trajectory would be about 1" above the line of sight and you could hold directly on target all the way out to about 125 yards. If the anticipated hunting distances are 200 yards or more, you should zero your rifle at the longer ranges. The MRT for a rifle zeroed at 200 yards is minimal for most cartridges (usually about 1.5" to 2") and you can hold directly on target for ranges out to slightly more than 200 yards. If a 200-yard range is not readily available, you can obtain a satisfactory 200-yard zero on a 100-yard range by zeroing about 1.5" high. A good rest, such as sandbags or steady rest to reduce sighting errors, will help you hold more steadily on target. Rest the forearm, not the barrel, on the rest. If possible, zero in a no-wind condition to establish a standard zero. If you must zero in a wind, make a note of the amount of drift attributable to wind effect and when finally zeroed, make a compensating adjustment to leave the scope at standard (no-wind) zero. For example: a 15MPH wind from the right at the 3 o'clock position will normally drift a .30-06 factory bullet about 1.5" to the left. When you have finished zeroing in a 15MPH wind, simply adjust the Windage knob 1.5" to the left. This will result in standard no-wind zero. The first time about 25 yards out from the muzzle. You can utilize this fact by firing your first zero shot at 25 yards target. If the first shot prints very close to the center of the bulls eye at this range, you can be confident that it will print on paper at 100 yards. If there is a significant error at 25 yards, make compensating changes to bring the point of impact to zero. Since the distance is only 1/4 of the 100 yard final zero distance, you will need to make 4 times as much adjustment as you would at 100 yards. For final zero, move the target to 100 yards (assuming this to be the desired zero distance) and fire at least 3 shots to establish a pattern. Using the center of this group as a reference, make any necessary adjustments to move the point of impact to center. You should fire another group of 3 shots to verify that this adjustment was correct. Do not trust a one-shot zero as accurate. Note: For maximum precision, allow the barrel to cool between shots. A warm or hot barrel shoots differently than a cold one. In the field a shot taken at game is usually from a cold barrel, so you will want to have your gun zeroed when cold. Making windage and elevation adjustments The elevation knob is marked "UP" with an arrow indicating the direction to turn the knob to move the point of impact up on the target. The windage knob is marked "R" with a similar arrow indicating the direction to move point of impact to the right. Many scopes have a graduated scale around the adjustment knob which increments representing a certain amount of point of impact movement on the target. The most common increment is 1/4 minute of angle which means one click or per increment adjustment moves the point of impact 1/4" at 100 yards. Per increment 25 50 100 200 300 400 500 1/2 MOA 1/8 1/4 1/2 1 1 1/2 2 2 1/2 1/4 MOA 1/16 1/8 1/4 1/2 3/4 1 1 1/4 1/8 MOA 1/32 1/16 1/8 1/4 3/8 1/2 5/8 Unit: Inch Eyepiece (Ocular) Adjustments Before installing the scope, you should set the focus of the eyepiece to fit your individual vision requirement. The ocular focus is pre-set for normal 20/20 visual acuity. Re-focusing the ocular distance will result in a sharper reticle focus, an improved optical image and avoid eye fatigue when using the scope over prolonged periods of time. To focus the eyepiece, loosen the lock ring and hold the scope about 3" to 4" away from your eye (12" to 16" for pistol scopes) and pointed at an unpatterned area such as the sky or a solid painted wall. If the reticle appears blurred when you first glance at it, it is out of focus or not focused for your eye. Turn the eyepiece counter clockwise a couple turns and glance at the reticle. It should be crisp and sharp to the quick glance (continued study allows the eye to adjust to an out of focus condition). Repeat this adjustment until you see the reticle crisply and clearly when you first look at it. Once eyepiece focus is adjusted, tighten the lock ring against the eyepiece to hold it in place. On some model scopes the ocular lens adjusts via a knurled ring at the end of the eyepiece. Follow the same procedure as above except there is no lock ring to tighten. Unless your eyes undergo a significant change in acuity over the years, you will not have to make this adjustment again. Note: Occasionally, the lock ring can be difficult to loosen. To loosen, simply hold the scope tube firmly with one hand and turn the eyepiece with the other hand. This will loosen the lock ring enough to be able to adjust. Parallax and Objective Focus Parallax occurs when the image rays from the object being viewed do not fall precisely on the reticle plane. Since a gap exists between the two planes, moving your eye off center to the edge of the exit pupil will produce an apparent movement of the reticle in relation to the target. If the eye is not moved off center in the exit pupil, parallax error cannot be discerned and there will be no PI (point of impact) shift in firing. When a scope is free from parallax, it is also at its best focus. Parallax is a negligible factor in scopes of hunting power and, since neither the average hunting rifle or factory ammunition is target accuracy, the effect of parallax is not deemed to be of significant importance to accuracy in typical hunting situations. However, parallax effect increases with an increase of power and the scope's depth of focus decreases. Therefore, in higher power scopes such as target scopes and scopes used for varminting, it is desirable to have some means for adjusting parallax/focus at all ranges as an integral part of the scope's optical system. The most of high power (more than 12 power) scopes have an adjustable parallax ring typically located on the objective bell. To set parallax focus, turn the objective parallax ring to the mark which corresponds to the anticipated or known shooting distance. To set parallax focus on the locking parallax adjustment scopes, loosen the parallax lock ring and turn the yardage indicator ring to the desired range. Be sure to tighten the lock ring Note: When a scope has been set free from parallax error at a specific range, some error, depending on magnification and distance to the target, will still exist at all other ranges, including infinity.