Canting means that you are dropping the barrels to one side or the other as the target approaches, or passes, your shooting position.
Ordinarily it’s classed as a fault and is most usually caused by an incorrect stance causing you to roll your shoulder as you run out of swing.
Canting the barrels in this fashion will often cause you to miss the bird or clay low but on some clay pigeon shooting targets it actually pays to cant the barrels before you start to move the gun and bring it to the shoulder.
Aim now is to keep the muzzles of the gun parallel to the line of the bird as it quarters toward you and then angles left or right over the gun line.
Birds like this can be notoriously difficult to deal with but the secret to shooting them is to watch really closely as they approach the peg and make your mind up as to what they’re doing BEFORE they come into range, then position your feet accordingly.
Trying to quickly readjust when they’re overhead is invariably a waste of time because you can’t get into a position which will prevent you running out of swing, pulling under the line of the bird and missing low.
My advice would be to find a shooting ground with a suitable high tower to practice, practice and practice before the next season starts.
That said, it’s also a very useful target for pigeon shooters to sharpen up on too.