There are two angles that must be met in order to optimize your chances of a detonation with an impact pistol: The vertical angle on the hull, and also the horizontal angle, as if you were looking down from above. With the vertical angle, the ideal is to strike the hull on its flat, perpendicular part. With the horizontal angle, the ideal is 90 degrees, but within 20 degrees is generally acceptable. Outside of these angles you risk deflecting off of the curved part of the hull/keel or striking at such an angle that the torpedo's impact whiskers are not struck. With magnetic pistols all you have to do is get the torpedo to sail under the keel, and any angle will do, even straight along the axis of the hull, but those are very difficult to achieve and the margin for success is very small. What makes magnetics so nice is that you can fire them from off angles and still have a detonation, as long as the pistol works.
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