Scope Leveler Device

As a measure in the process of eliminating—or at least reducing—the effects of accuracy-robbing scope canting, we can install a scope leveling device designed for the purpose. These levelers are for sale and range widely in price, or we can conveniently make them from readily-available materials. This will be the approach covered in this treatise. As a rifleman and gunsmith, it behooved me to determine precisely how rifle canting actually affected bullet impact on target.

Some years ago, and more recently, I conducted definitive tests to reveal the effects Top This high-height scope base works out perfectly for the 3/8 x 1" level used. The existing base hook was removed from the ring. Bottom of rifle sight canting. As a scoped rifle is shot, the sight reticle (crosshairs) should be perpendicular to the aim point on target, or as uniform as possible from shot to shot.

Under normal shooting conditions a shooter can arrive fairly close to maintaining a vertical and horizontal scope reticle without canting error, but it seldom occurs. Errors here are more critical while target shooting or shooting game at long range. The insidious effects of scope rotation can creep in as the shooter aims and shoots the rifle from shot-to-shot.

high-height scope ring has been prepped for use as a scope leveling device. Shown is a 30mm ring with optional reducer shims for a one-inch scope tube. Upper ring is a 30mm Redfield Jr. Other two are inexpensive rings machined and ready for use. Depending largely on the height of the scope above bore axial center and the ammunition used, as little as a few degrees of cant can cause the bullets to impact from the intended aim point. Where the rifle is canted right, the bullet will hit right and low of aim.

Alike deviation occurs where rotation is left. While not dwelling on a lot of geometric technicality, I’ll elaborate on the harmful effects of canting a riflescope as we shoot and show how to make proper corrections. Canting error on target occurs when the barrel axis is rotated out of the vertical plane.

As a scope is mounted well above the bore axis, the bullet must cross the line of sight at about 25 yards and then again cross the line of sight at the point Below center: The proper procedure for attachment of a scope leveling device is quite basic, but must be performed with precision. First the rifle is carefully leveled. A common bubble level is used here across the Picatinny rail. The scope leveling device is then leveled into place.

This scope is mounted quite high above the bore line which would increase the effects of rifle canting. where the rifle is sighted in. This sets the stage for right or left impact errors depending on how much the barrel is canted out of the vertical plane. Cant rotation causes the bullet to impact in the direction of rotation with at least some drop as an effect of trajectory. In all cases, canting a rifle will be harmful to precision and accuracy, but there are corrections that can be made to alleviate this.

Making A Scope Leveler Device The pictures will serve as a guide in making a scope leveling instrument. As apart to hold the level used in making the leveling device, I used a common Redfield Jr. high-height ring. A front or rear ring will suffice. I also used a pair of aluminum rings of another style with a sufficiently high base for the same purpose. Either one-inch or 30mm scope rings can be used. A 3/8-inch hole was drilled and reamed at center on the underside of the base to about 1/2-inch depth.

Four small set screws were drilled and tapped around the bottom pe-

The three shots marked zero (left) show a 2 3/4" bullet shift (right) as the scope is canted 5 degrees at 300 yards. This is no small error for the serious target shooter. rimeter of the base to hold the inchlong 3/8" diameter spirit level. With level inserted to desired depth, the four set screws are lightly tightened. The level is essentially self-aligning in the base hole.

Attaching To The Rifle When installing a leveler, always begin with the rifle held precisely perpendicular in sand bag rests or other method of holding. There must be no cant or rotation right or left. This requires some attention to detail, which can be deceptive. The rifle must be precisely aligned with a level, not just by eye. A perpendicular line on a paper attached to the butt plate will work fine after checking with a small machinist’s level.

The next critical step is to align the scope reticle precisely perpen- Cant error is shown in the direction of cant. Cartridge and load used was a 6x45mm with 88 grain bullets at 2540 fps. The bullet type and velocity as well as the height of mounted scope above bore axis has an effect on the cant error. dicular with the squared rifle. If this isn’t accomplished, the scope reticle will be at an angle with the rifle.

This can be checked out by aligning the scope reticle with a known object that is level or perpendicular. The rifle must therefore be kept in a perpendicular position as the scope is leveled. With the rifle maintained in true vertical position, the leveling device is attached with the level bubble at true level. The modified rings used as the leveling device can be clamped to the scope just ahead of the rear ring on either side of the scope.

While it is easier to see on the left side of the rifle, it is less likely to be damaged while carrying the rifle if attached to the right side. Double check the perpendicular position of the rifle and scope reticle as necessary from time to time. So now we have the rifle, the scope reticle, and scope leveler device all calibrated, leveled, and ready to put to the test. I made up a special target using an angle rule to indicate the position of the scope reticle in degrees of perpendicular alignment.

This test target makes it possible to aim the rifle to the exact degree off level shot-to-shot. The degree of shot displacement or error on target will depend on scope height above the bore line, bullet trajectory, and distance. Bullet impact will vary. This leaves nothing to guesswork. Conclusion While adding a leveling device to a rifle may not improve its inherent accuracy, it will alert us to the effects of accuracy-robbing cant. If we can nullify this untoward problem, groups are sure to improve.

AG When shooting a rifle, it is not always easy to distinguish cant error differences. A scope leveler device takes the guesswork out of the equation.