A SIGHT LEVELING CONCEPT
By Gene Lueck
What is a bow sight? A bow sight is a piece of equipment we attach to our bow which enables us to program the drop of an arrow to hit a target at a given distance. By moving the block of your sight up or down, you can change the impact of your arrow from near to far and back again. This is what I want to talk about.
Since we are dealing with the effect of the force of gravity on the arrow, there are several factors that we must deal with in order to also control the left or right impact of the arrow.
Due to the fact that gravity ALWAYS pulls the arrow STRAIGHT down from the time the arrow leaves the bow until it hits the target, it is absolutely necessary to have your sight bar perfectly parallel to gravitational pull. In order to achieve this relationship it is necessary to set your level bubble with a considerable amount of accuracy. I am going to describe a method that will assure you of this type of accuracy.
Over the years people have used various methods which may or may not have worked, such as the old pillar in the basement, the doorjamb in the hallway, or the side of a tree in the front yard with a carpenters level. These methods have gotten us by over the years but have always left a little to be desired. Given the technological advancement of today's equipment and the ability of today's archers those old methods are not acceptable.
It is necessary to hold your sight in a rigid fixture, which will enable you to pivot it in a perfectly vertical arc up and down. You must remove your sight block from the sight bar before starting this procedure, or move the block to one end so you can place a torpedo level against the flat side. Adjust the fixture so the sight extension is parallel to the ground. Place a torpedo level vertically on the side of the sight bar, and loosen the two screws that attach the sight bar to the sight extension. Adjust the sight bar until the torpedo level indicates that it is vertical and tighten the screws. Re-check with the level to make sure that the bar didn't move when you tightened the screws.
At this point you can place your sight block on the sight bar or move the sight block to a point adjacent to the end of the extension and set the level bubble. All quality sights on the market today will have adjustment screws to enable you to set the level bubble. Now is when you must pivot your sight upward or downward to determine if the sight aperture screw is at right angles to your sight extension. First point the sight upward at about a 30-degree angle and see if the bubble stays centered. If it does not, you may need to adjust the third axis, you may need to slightly shim the mount that the sight screw runs through, or adjust the level bubble itself, as some apertures have this feature on them. Looking from the front of the sight, if the bubble is to the right, you must place the shim vertically under the left side of the mount and vice versa. (Left hand would be the opposite) Then point the sight horizontally again. At this point the bubble should be centered. Now point the sight downward 30 degrees and check the bubble again. Due to the fact that the vials that are used for level bubbles are not necessarily perfectly shaped, sometimes it is necessary to alternate the up and down movements and make very slight adjustments to ultimately center the bubble in all areas of the 60 degree arc. During this upward and downward check, DO NOT LOOSEN THE LEVEL ADJUSTMENT SCREWS ON YOUR SIGHT BLOCK. Except to shim the mount if necessary. Always do this with the sight bar horizontal. Once you have these screws set you should never touch them again unless you replace the sight aperture.
Your level bubble is now properly adjusted.
Now lets put the sight on the bow. Contrary to popular belief it is not necessary to align your sight bar with the string. I would ask you if you have ever seen a crossbow with the sight bar aligned with the string? Simply attach the sight mount to the bow and place the sight in it. Tighten down the sight knob and draw the bow. If the level does not feel comfortable it is totally acceptable to cant (lean) your bow. I personally cant my bow between 3 and 5 degrees to the right as I am right handed. This cant should be a point at which you are comfortable at full draw. You can determine this point by closing your eyes, drawing the bow, opening your eyes and checking the position of the level. Since we have set the level bubble in relation to the sight bar, you must not loosen the screws on the sight block but in stead, loosen the screws that attach the sight bar to the sight extension. Once these screws are loosened, you must experiment by canting the bar one way or the other and tightening the screws until the bubble is in the middle and you are comfortable at full draw.
Now we have the sight attached to our bow and are able to aim up or down hill and maintain a level bubble.
The final item that we must cover is the relationship of the sight bar to the arrow. It is imperative that the level bubble vial is at right angles (perpendicular) to the path of the arrow. In order to achieve this, it may be necessary to place shim material beneath your sight extension mount, either in back or front of the screws vertically to square the arrow with the front of the sight bar. It is necessary to have a small carpenter's square to check this. Place an arrow on the string and across the arrow rest with the bow held vertically. Place the carpenters square across the front of the sight bar and align it with the arrow shaft. If this alignment indicates that the arrow is not traveling at right angles to the front of your sight bar, you will need to properly shim your sight mount block to achieve this.
Now we have a sight attached to our bow, we are comfortable at full draw, and the arrow is traveling at right angles to the bubble. With this set-up you will have the ability to shoot up hill or down hill, long or short distances, and the impact of your arrow will not vary from left to right. The rest is up to you.