A pellet always starts at a speed relative to the stationary muzzle. But reference the air around it, it quickly adopts different groundspeeds.

A 15 mph headwind will subtract 22fps from the effective muzzle velocity (reference the ground speed)

A 15 mph tailwind will *add* 22fps reference the groundspeed

These are maximum figures, and practical effect is somewhat less that this in both cases, but no matter. We'll analyze using max effect.

The standard 20ft-lb Crosman Premier start outs at 830fps, and when zeroed at 25 yards strikes 28" low at 100 (no wind).

With the 15mph headwind, it will find itself adopting an apparent 808fps initial groundspeed, and impact 30" low at 100.

The 15mph tailwind will cause an apparent increase in groundspeed to 852fps at the muzzle, and hit 26" low at 100.