Cant test

The following test was designed to illustrate the results of canting a scoped rifle. Targets were shot with airgun, smallbore, and highpower rifles at preprinted targets designed to help the shooter intentionally introduce a known cant.

Definitions:
Cant:
any deviation from a vertical hold position.
Vertical hold: where the scope is held directly above the barrel.

Background

Cant errors have long been known to produce fliers and inaccuracy. Tilting the firearm generates cant error that produces inaccuracy for shooters, especially in competition and long-range hunting. A remedy has been to use an externally mounted bubble level. Some shooters find this acceptable but most find it too difficult to be useful. This test shows the shooter how to identify what the error looks like and how much error is produced.

Test Procedure

Each test was designed to explore the ranges commonly used for that type of rifle. Custom targets were designed and printed with computer to assure repeatable and measurable results. The target was designed with a heavy crosshair rotated about the target center by either 10 or 20 degrees. The method of determining the cant was to set the top target edge horizontal with a carpenters level during setup. The rifle scope is then rotated to line up the retical with the printed bold rotated crosshairs on the target. For the longer range shots where the target was too small to see the rotated lines we used the Microlevel to hold a repeatable position. The level was set in its most sensitive range. A gravity inclinometer was used to reset the zero point on the Microlevel®. By holding the Microlevel on the green indicator we are assured that the rifle is canted to the same value each time. Each rifle was fired at three different distances, a short, medium and long range.  Each rifle was zeroed at the sighter target with a 5 shot group. Additional 5 shot groups were fired with the rifle canted 10 degrees and 20 degrees. While twenty degrees is a bit extreme, it gives results that clearly illustrate the problem. No one associated with this test believes that you could cant 20 degrees and not know it. 10 degrees might be possible and 5 degrees seems like no cant at all.

Equipment Used

    Airgun: Anschutz 2002 .177 Cal. Airgun (Modified By Allen Zasandny)
    Ammo: Crosman Premier Pellet Wt. 10.5 grains
    Velocity: 875 FPS
    Scope: 36x Nightforce

    Smallbore: Feinwerkbau 2602 .22 LR Caliber
    Ammo: RWS Rifle Match
    Velocity:1012 FPS
    Scope: Leupold (Premier Modified) 8.5x35X

    Highpower: Remington 40x Hart Barrel
    Ammo: Winchester Varmint extreme Silver ballistic tip 40 grain
    Velocity: 
    Scope: Nightforce 8-32

Ranges Fired

    Airgun 30, 50, 55 Yards
    Rimfire: 50, 100 Yards
    Highpower: 200, 300, 600 Yards

Results

All grid squares are ½” on test targets

Airgun (.177):

    30 Yards 10 Degrees Right Cant; Produces .5” Right .12” Drop Error


    30 Yards 20 Degrees Right Cant, Produces .6” Right .12” Drop Error

    50 Yards 10 Degrees Left Cant, Produces 1.35” Left .2” Above Error

    55 Yards 10 Degrees Left Cant, Produces 1.45” Left .25” Drop Error

    55 Yards 20 Degrees Left Cant, Produces 2.9” Left .62” Drop Error

Rimfire (.22):

    50 Yards 20 Degrees Left Cant, Produces 1.81” Left .6” Below Error

    50 Yards 3 Groups, 0 Degrees, 10 Degrees, 20 Degrees on Same Target Shows Progressive Nature of Error

    100 Yards Right Cant 0 Degrees, 10 Degrees, 20 Degrees, 0 Degrees is a bit to the left of center with one low flyer (my fault), 10 Degrees right cant, produces 3” right – it is a wide group because there was no 10 degree line – resulting in a best guess on the 10 degree cant amount, 20 Degrees Right Cant, Produces 5.3” Right .5” Drop Error

    100 Yards Right Cant Error at 2.5 Degrees using Microlevel® on
    red/yellow setting.
    1.3” Right .6 Drop Error

    Highpower:Results available soon.

 

[Home] [Features] [Cant Errors] [Level Story] [Setup Install] [Order] [Contact Long-Shot]

 

Any re-publication or  commercial use of this material by others is prohibited without written approval of
Long-Shot Products LTD