Air Gun Guru: Scope Cant
PUBLISHED: 11:20 31 May 2016 | UPDATED: 11:20 31 May 2016
Q: One of the topics that most frequently crops up in readers' letters is scope cant; what it is, and what its effects are. Can you please write a simple layman's explanation? The Editor.
GURU SAYS: What everyone refers to as ‘scope cant’ is actually rifle cant, or the rifle being held at a slight angle, rather than being perfectly vertical, and this moves the centreline of the rifle and the axis of the barrel to one side of the sight line. If the rifle is canted to the left, the barrel moves to the right of the sight line, so in order to cross the sight line at the first crossing point (the near zero), the pellet has to move from right to left.
Having reached the crossing point, the pellet then carries on to the left of the sight line, and the further it travels from the muzzle, the further to the left it travels. In addition to the left/right pellet travel, canting the rifle also reduces the amount by which the barrel is pointing upward to counteract gravity, and so the pellet lands low in addition to being one side or the other of the sight line.
In fact, if a single shot unexpectedly lands low and to one side, and in the absence of any obvious explanation such as a very strong gust of headwind, rifle cant is nearly always the culprit.
For most of us, rifle cant will only occur during a few occasional shots, causing the odd pellet to land low and to one side, but some people habitually cant their rifle, and there is an easy test to diagnose this.
When the rifle is held vertically, the pellet will be bang on target at two distances, the near and far zero, but if the rifle is habitually canted, there will only be one distance at which the rifle is perfectly zeroed, and at all other ranges, the pellet will land to the side of the sight line.
Some target shooters fit spirit levels to their rifles or scopes to check that they’re vertical, although for most of us, being aware of the possibility of rifle cant and taking care to keep the rifle upright will be enough to ensure that any cant will be so slight that its effect will be insignifi-cant.
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