Effects of zeroing distance on trajectory (75OTM)

EFFECT OF ZEROING DISTANCE ON BULLET TRAJECTORY: 75gr OTM @2650fps

This post is written to illustrate the effect that the distance your rifle is zeroed at has on trajectory. Molon has already done a great job, but there were questions about some intermediate distances. I also want to thank lazyengineer for giving me the idea to write this FAQ as he pretty much went through the same exercise.

In this example, I used a 75gr Hornady OTM at a muzzle velocity of 2650fps, AR15 sight height of 2.6" (same as iron sights and cowitnesses red dots and such). The bullet choice was merely to obtain a valid BC, and the muzzle velocity approximates the velocity halfway between Hornady's TAP-FPD .223 and 5.56 loads out of a 16" rifle.

NOTE: Before you ask about bullet X out of barrel Y and velocity of Z, be aware that the changes will be relatively minor from the example below. Ultimately, you should still confirm that your own rifle will shoot as projected. There is no substitute for doing this yourself. This guide is merely to show you what your options are so that you can choose what works best for you.

A good concept to think about is "point blank" range. This is the range at which you can shoot at a target (within the chosen parameter of variance) and not adjust your aim. For example: Let's use 5" as your degree of variance; the point-blank range of the 37.5 yard zero is approximately 290 yards. For a 2" variance and the 50 yard zero, your point blank range is 255 yards.

First is the 400 yard range trajectory:



You might be surprised to see that the bullet trajectory for the 25 yard zero rises 8+ inches above the line of aim at its apex! The bullet doesn't re-cross the line of sight until about 330 yards!

Zoomed in on the 200yard range:



As you can see, there's not a whole lot of difference in the intermediate zeroing distances.


And finally, the raw data in PDF form: http://www.ar15.com/media/viewFile.html?i=26779

The data is shown in 10 yard increments, but the trajectory is nearly linear within that range, so you can easily interpolate to any distance in between. For example: What is the trajectory at 25 yards with a 50 yard zero? We have -1.41" @20 yards and -0.89 @30 yards. Therefore, the 25 yard trajectory is (-1.41 + -0.89) / 2 = -1.15"

  Range    25yd  37.5yd    50yd  62.5yd    75yd   100yd   150yd   200yd   250yd   300yd Velocity
       0   -2.60   -2.60   -2.60   -2.60   -2.60   -2.60   -2.60   -2.60   -2.60   -2.60    2650
      10   -1.52   -1.84   -1.98   -2.05   -2.09   -2.10   -2.05   -1.94   -1.80   -1.64    2622
      20   -0.50   -1.13   -1.41   -1.55   -1.62   -1.66   -1.54   -1.32   -1.05   -0.73    2600
      30    0.48   -0.46   -0.89   -1.10   -1.21   -1.26   -1.09   -0.76   -0.34    0.13    2577
      40    1.41    0.15   -0.41   -0.70   -0.84   -0.91   -0.68   -0.24    0.31    0.94    2555
      50    2.28    0.70    0.00   -0.36   -0.54   -0.62   -0.34    0.21    0.90    1.69    2533
      60    3.09    1.20    0.36   -0.07   -0.28   -0.39   -0.04    0.62    1.44    2.38    2510
      70    3.86    1.65    0.67    0.17   -0.08   -0.20    0.20    0.97    1.94    3.03    2488
      80    4.57    2.05    0.92    0.35    0.07   -0.07    0.39    1.27    2.37    3.62    2467
      90    5.21    2.38    1.11    0.47    0.15   -0.01    0.51    1.50    2.74    4.15    2445
     100    5.80    2.65    1.24    0.53    0.18    0.00    0.58    1.68    3.05    4.62    2423
     110    6.33    2.86    1.31    0.53    0.14   -0.05    0.58    1.79    3.31    5.03    2402
     120    6.80    3.02    1.33    0.47    0.05   -0.16    0.53    1.85    3.50    5.38    2380
     130    7.21    3.12    1.29    0.37   -0.10   -0.33    0.42    1.85    3.64    5.68    2359
     140    7.55    3.14    1.17    0.18   -0.32   -0.57    0.24    1.78    3.70    5.90    2338
     150    7.84    3.11    1.00   -0.06   -0.60   -0.86    0.00    1.65    3.72    6.07    2317
     160    8.05    3.01    0.76   -0.37   -0.94   -1.23   -0.30    1.46    3.66    6.17    2296
     170    8.20    2.85    0.45   -0.75   -1.36   -1.66   -0.68    1.19    3.53    6.19    2275
     180    8.29    2.62    0.08   -1.19   -1.83   -2.15   -1.11    0.87    3.34    6.16    2255
     190    8.29    2.31   -0.37   -1.71   -2.39   -2.73   -1.63    0.46    3.07    6.05    2234
     200    8.24    1.94   -0.87   -2.29   -3.01   -3.36   -2.20    0.00    2.75    5.88    2214
     210    8.12    1.50   -1.45   -2.94   -3.69   -4.06   -2.85   -0.54    2.35    5.64    2193
     220    7.92    0.99   -2.11   -3.67   -4.46   -4.84   -3.57   -1.15    1.87    5.32    2173
     230    7.64    0.40   -2.84   -4.47   -5.29   -5.70   -4.37   -1.84    1.32    4.93    2153
     240    7.29   -0.27   -3.65   -5.35   -6.21   -6.63   -5.24   -2.60    0.70    4.46    2132
     250    6.87   -1.01   -4.53   -6.30   -7.19   -7.63   -6.19   -3.44    0.00    3.92    2112
     260    6.36   -1.83   -5.49   -7.33   -8.26   -8.72   -7.21   -4.35   -0.78    3.30    2093
     270    5.78   -2.72   -6.53   -8.44   -9.40   -9.88   -8.32   -5.35   -1.64    2.60    2073
     280    5.12   -3.70   -7.64   -9.63  -10.63  -11.12   -9.51   -6.42   -2.57    1.82    2053
     290    4.37   -4.77   -8.85  -10.91  -11.94  -12.45  -10.78   -7.59   -3.60    0.94    2033
     300    3.54   -5.91  -10.13  -12.26  -13.33  -13.86  -12.13   -8.82   -4.70    0.00    2014
     310    2.62   -7.14  -11.51  -13.71  -14.81  -15.36  -13.57  -10.16   -5.90   -1.04    1995
     320    1.62   -8.46  -12.97  -15.24  -16.38  -16.94  -15.10  -11.57   -7.18   -2.16    1975
     330    0.52   -9.87  -14.52  -16.86  -18.03  -18.62  -16.71  -13.08   -8.54   -3.37    1956
     340   -0.66  -11.37  -16.16  -18.57  -19.78  -20.38  -18.42  -14.67  -10.00   -4.67    1937
     350   -1.94  -12.97  -17.90  -20.38  -21.62  -22.24  -20.22  -16.37  -11.56   -6.07    1918
     360   -3.31  -14.65  -19.72  -22.28  -23.56  -24.19  -22.12  -18.15  -13.21   -7.56    1900
     370   -4.78  -16.43  -21.64  -24.27  -25.58  -26.24  -24.10  -20.03  -14.94   -9.14    1881
     380   -6.35  -18.32  -23.67  -26.37  -27.72  -28.39  -26.20  -22.01  -16.79  -10.83    1863
     390   -8.01  -20.30  -25.79  -28.55  -29.94  -30.63  -28.38  -24.09  -18.73  -12.61    1844
     400   -9.79  -22.39  -28.02  -30.85  -32.28  -32.99  -30.68  -26.27  -20.78  -14.51    1826
     410  -11.66  -24.57  -30.35  -33.25  -34.72  -35.44  -33.07  -28.56  -22.92  -16.50    1808
     420  -13.64  -26.87  -32.79  -35.76  -37.26  -38.00  -35.58  -30.95  -25.18  -18.60    1790
     430  -15.73  -29.27  -35.33  -38.37  -39.91  -40.67  -38.18  -33.45  -27.54  -20.80    1772
     440  -17.93  -31.79  -37.98  -41.10  -42.67  -43.45  -40.91  -36.06  -30.02  -23.12    1754
     450  -20.24  -34.42  -40.75  -43.94  -45.55  -46.34  -43.74  -38.79  -32.60  -25.55    1737
     460  -22.67  -37.16  -43.64  -46.90  -48.54  -49.35  -46.70  -41.63  -35.31  -28.10    1719
     470  -25.22  -40.02  -46.64  -49.97  -51.65  -52.48  -49.76  -44.59  -38.13  -30.76    1702
     480  -27.88  -43.00   79.00  -49.76  -53.16  -54.87  -55.72  -52.95  -47.66  -41.07    1685
     490  -30.67  -46.11  -53.01  -56.48  -58.23  -59.09  -56.26  -50.87  -44.14  -36.45    1668
     500  -33.59  -49.34  -56.38  -59.92  -61.70  -62.59  -59.70  -54.19  -47.32  -39.48    1651