A. The horizontal effect of canting is related to
1. The distance the point-of-impact differs vertically from the point-of-aim (POA) and the point-of-impact. (POI)
2. The amount of cant, in degrees from the vertical.
It is calculated by multiplying the inches the POI is away from (above, conventionally) the POA times the sine of the angle of tilt.The product is the horizontal distance the POI moves to the left for a anticlockwisei tilt or right for a clockwise tilt.
B. The vertical effect of canting is also related to
1. The distance the point-of-impact differs vertically from the point-of-aim and the point-of-impact.
2. The amount of cant, in degrees from the vertical.
It is calculated by multiplying the inches the POI is away from (above, conventionally) the POA times the cosine of the [angle 90 degrees minus the angle of tilt.] The product is the vertical distance the POI is now depressed from (above, conventionally) the original POI. It is independent of the question whether the tilt is clockwise or anticlockwise.
That is, it has nothing to do with all the construction details of the gun that seem like they must affect it: over-barrel vs under-barrel. high ribs, unsingles, whatever.
The lucky thing is that the sine changes little when its value is near zero degrees and the cosine is similarly stable around 90 degrees.
Horizontal POI change:
For example, let's consider a gun with a POI 5 inches above the POA at a certain distance and which the shooter cants 10 degrees:
The sine of 10 degrees is 0.17 and 0.17 x 5 = 0.87 inches. That's how far the POI of that gun, shooting 5 inches high, will be moved to the side with a cant of 10 degrees. Even a gun which shoots 10 inches high at a certain distance and canted 10 degrees will only move twice that right or left, about an inch and a half.
Vertical POI change:
Again, we are talking about a gun which shoots 5 inches high at a certain distance and the angle of cant is 10 degrees.
When you subtract the angle of tilt, 10 degrees, from 90 degrees you get 80 degrees. When a gun that shoots 5 inches high at a certain distance is canted 10 degrees it will now shoot 0.87 inches lower, that is, 4.1 inches high, no matter in which direction the gun is canted,
Jezek
Yes, Alan Rhone has this wrong (in print) , just as I think he has the effect of comb height wrong elsewhere in this forum.
