Nearly every new airgunner seems to prize velocity over everything else. As soon as they discover air rifles can exceed 1000 fps, they automatically want it, conveniently disregarding all the compromises that make it possible.
1300 Feet Per Second
Make no mistake, velocities of 1300 fps are possible in an air rifle. I have personally seen 1380 fps from a precharged (PCP) AirForce Condor shooting lightweight .177 Skenco pellets with synthetic skirts. So, what’s the problem?
There are several. When a pellet breaks the sound barrier, the sonic boom is heard as a sharp crack. Airgunners like shooting quietly, and this secondary crack is anything but!
The diabolo pellet is characterized by a wasp waist and a flared hollow tail. These two features create high aerodynamic drag that stabilizes the pellet when launched at subsonic velocities.
The greatest objection, however, is the lack of accuracy. A diabolo pellet (wasp-waisted, hollow flared skirt) is a high-drag projectile, designed to fly at subsonic velocity. As it nears 1000 fps, the pressure wave that forms on the nose and flows back around the wasp waist causes the flared hollow tail to flutter.
That can destabilize the pellet in flight. The farther the pellet has to travel, the greater the destabilizing influence. So, while a group of supersonic pellets at 30 feet might appear just as accurate as a group of slower pellets, at 50 yards there can be a dramatic difference.
A related velocity issue is the transition from supersonic back to subsonic. Target .22 long rifle target ammunition is made to exit the muzzle at subsonic velocity. Ammunition manufacturers learned that when a bullet transitions from supersonic to subsonic, it gets buffeted.
A solid lead bullet that starts supersonic at the muzzle and transitions to subsonic at 75 yards is not going to group as well at 100 yards as the same bullet that remains subsonic the whole way.
A badminton birdie or shuttlecock has much in common with the diabolo pellet. The high-drag skirt keeps the soft rubber end pointed forward in flight. Neither is intended for high velocities.
Switching back to airguns, a diabolo pellet is not intended for supersonic flight. It owes a large part of its stability to its high drag. Think of it as a badminton birdie. Even if it starts out at 1300 fps, the brakes are on the moment it leaves the muzzle. It will drop subsonic before traveling 75 yards.
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