All replies above are good advice and explanation of what may be going on....
I would add that most air gun shooters tend to look for a pellet stabilization similar to how a bullet is stabilized in a rimfire or certerfire gun...
There are many similarities yes, both projectiles need to rotate in order to induce a gyroscopic stabilizing motion, both tend to wobble a little upon leaving the barrels and before fully stabilizing and do the same when the velocity drops below certain level, both "Yaw" under certain parameters, etc...
But what most people don't take in consideration is that pellets are designed to stabilize the very same way a Badminton Fly does...So if someone wants to emulate what a pellet does upon leaving a barrel, get a racket and a fly and see for yourself...Yes, I know...There are pointed pellets that don't have the "Round" typical pellet head but those are also stabilized with barrels designed for the pellets we are talking about...
This badminton stabilization effect is what makes deep rifling and fast barrels unnecessary unless you want to shoot projectiles that resemble bullets as used in rim & center fire guns. These guns require a barrel with a twist calculated to stabilize the projectile being used and a barrel with a rifling ratio (groove to land ratio)just enough to grab the bullet while minimizing bullet deformation .
Spiraling - Yawing can be caused by many variables: Damaged crown, longer projectile that what the barrel is designed to stabilize, pellet too light, worn or damaged rifling, not enough engraving or too much, etc.
You can do your own research: Shoot some pellets at a distance to a water container and recuperate those pellets, check around the head and the skirt for deformations - deep engravings, etc...Do the cotton swab test to the crown: Gently Introduce a Q tip through the crown and pull the Q Tip out and then look for fine cotton fibers trapped by the burs around the crown (use a magnifier)...Check for a dull crown (A burred crown and a dull crown provide the same effect).. A loose pellet can also cause yawing, check the gun with other pellets....Too much power in a lighter pellet induces yawing as well....etc...
Regards,
AZ
