Effect of BC on subsonic bullets

[Expatriot]

Many subsonic rifles can easily reach 1000 yards with lethal energy.

There is a big difference between reaching a distance and being able to hit the target you are shooting at.

The effective or practical range of a bullet or cartridge combination is the distance at which you can hit the thing you are aiming at. The energy the bullet is carrying is pointless if it doesn't hit the target.