Posted On: 10/19/11 By: Rick Pearce
Subsonic ammo uses a heavier, slower bullet that will not break the sound barrier. It will still travel very far, but will drop more at longer ranges (say, 100 or 200 yards). This is not an issue for most people, but if you are shooting that far, you can simply correct for the greater bullet drop by aiming slightly higher.
Another consideration is practice for the use of defensive ammo - if you carry or use 147gr 9mm ammo for home defense, you might want to use 147gr ammo for practice and training use.