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	 The zero that will give the fattest span of ranges over which a directly aimed (i.e., no holdover or holdunder) shot will have a point of impact (POI) close enough to the point of aim POA to get the job done -- i.e., a hit inside the vital zone of the target in question.
	The technical term for this is "Optimum Point Blank Zero" (OPZ).
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 	"Trajectory Apogee" = range to the highest point in the trajectory = where the pellet kisses the top edge of the vital zone:
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	Apogee_yds = MV x square_root(SH + VZR) / 45
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"Secondary Zero"(SZ) = range where the pellet first crosses the line of sight on its way up to the apogee: 
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SZ = MV x [square_root(SH + VZR) - square_root(VZR)] / 45
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	"Point Blank Range" (PBR) = range where the pellet drops below the vital zone in its decent from OPZ -- the max range to a direct shot:
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	PBR = MV x [square_root(SH + VZR) + square_root(2 x VZR)] / 45
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	"Near Point Blank Range" (NPBR) = range where the pellet first rises to the bottom edge of the vital zone in its aceent to the SZ -- this is the minimum range for a direct shot:
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	NPBR = MV x [square_root(SH + VZR) - square_root(2 x VZR)] / 45
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	Caveat: These simple formulas are only approximate because none fully incorporates the effect of air drag. They instead assume a ballistically efficient pellet (BC > 0.02) and incorporate a number of fudge factors. They also assume SH > VZR which is seldom true in powder burners but (almost) always true in airgunning. They work reasonably well under those limitations and provide at least a useful starting point.
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	Steve_in_NC
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