[B.L.E.]

Explanation for my previous post:
The speed of sound is 1125 fps when the air temperature is 68 degrees F. 1200 fps is faster than that so a pellet going that fast will make a sound similar to the cracking of a whip.
The familiar sound of a .22 rifle is mostly due to the sound that the supersonic bullet makes when going through the air.

If you don't hear that whip cracking sound when you shoot, your pellets are going slower than the speed of sound. Those advertised velocities are based on velocities using pellets made of extra light copper or zinc based alloys. Regular lead pellets will go slower, but will retain their velocities better so even though they are slower at the muzzle, they may actually be much faster at 25 or 50 yards.

I'm just saying, don't take those velocity claims too seriously, there's a lot of puffery in advertising. I have one air pistol that's supposed to shoot 400 fps, I also have a chronograph and it says about 350 fps.

Also, spring-air pellet guns are extremely sensitive to how they are supported and putting them on a hard rest can really open up the groups. There is a lot of gun movement when the spring piston fires and if the gun is not supported exactly the same way every shot, the gun movement during firing will not be exactly the same, and this will change the point of impact.
If you are going to use it offhand, sight it in shooting offhand.