In both reality and common sense theory, a 1 inch group at 100 yards will open up at least 10% for each additional 100 yards of range. It's caused by the spreads of muzzle velocity, bullet BC (small spread caused by bullet unbalance) and air movement in the trajectory. And for each 100 yard range band, the percentage increases. For example, vertical shot stringing at 100 yards with a 50 fps muzzle velocity spread from a .308 Win is about 1/10th inch. At 600 yards, it's 4 to 5 inches. At 1000 yards, it's around 20 inches.
All this without bullet drop compensation. If bullets leave the muzzle on its axis upswing such that slower ones depart at higher angles, long range groups will be smaller in MOA than mid range ones.
Last edited by Bart B.; October 24, 2014 at 11:14 AM.
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