Subtending

Subtending, as Webster refers, is associated with geometry. Also this term is used to describe the use of mental geometry which is helpful in quickly estimating the range of a (known size) distant object. Imagine comparing the size of your shotgun front sight bead or the width of your shotgun muzzle to a bird at a distance. Using a sketch of or a full body decoy, place the full sized “target” at a typical shooting range. Example, if we are planning to shoot puddle ducks over decoys and we wish to ideally shoot from 20 to 30 yards away, set your training decoy at about 25 yards distant (midway in your desired range for this training exercise). Also place a second training decoy at your desired maximum range, so for this example, let us presume 40 yards distant. Mount your shotgun and point it at the (25 yard) training decoy, keeping both of your eyes open as you typically do when actually shooting. Study the size relationship of the front bead / muzzle diameter as compared to the size of the training decoy. Carefully study this size relationship at the 25 yard decoy. Now, swing to the 40 yard decoy and notice how remarkably much smaller the decoy is as compared to the front bead and / or the muzzle diameter. In fact, the distant decoy might easily be completely covered by the muzzle if you chose to do so. Practice back and forth repeatedly, firmly etching those two size relationships in your short term memory. The close bird looks much bigger, so you will easily recall the width when OK to shoot… the more distant bird will require much more lead due to time in flight of the shot string. Simply being more aware of the active distance/ velocity / lead concerns will immediately make you more aware of better shooting habits.