Effect of BC on subsonic bullets

[LouBoyd]

This chart might be of interest. Here are the ranges which a bullet fired at 1000 fps will drop to 800 feet per second as a function of it's Ballistic Coefficient (BC). It assumes the target is at the same elevation as the rifle and the atmosphere is standard metro. These are G1 BCs in the 800 tps to 1000 fps range (as calculated by McDrag). Dropping from 1000 to 800 fps retains 64% of the muzzle energy for any bullet. The chart is not dependent on bullet weight or caliber (though BCs are).

BC yards for velocity to drop from 1000 fps to 800 fps
1.0 1520
0.9 1360
0.8 1180
0.7 1080
0.6 860
0.5 720
0.4 580
0.3 420
0.2 280
0.1 140

To me this indicates the minimum BC requried for various ranges of subsonic shooting. You can choose a smaller or larger value for acceptable energy loss. The maximum practical range can also be limited by wind deflection and vertical stringing due to muzzle velocity variations. All three need to be conisdered.