One quick add to Jimro's info.
The transonic range is from .8 mach to 1.2 mach. These numbers are not hard numbers due to differences caused by temperature and pressure but they are the numbers aeronautical engineers work with and are a good guideline. Between these numbers you have air flow that is both sub. and supersonic and that causes erratic turbulence around the projectile as well as a traveling shock wave in front of the moving object. Some projectiles (aircraft or bullets) handle this transition better than others.
Match 22 ammunition is usually loaded to leave the barrel at 1050 fps. or less or approximately .95 mach. The shape of these bullets handles the speed well and they drop out of the transonic velocity range quickly; usually about 50 yards out. High velocity 22 ammo. at 50 yards is solidly in the transonic range at this distance.