using fins longitudinally-slidable with respect to the projectile or missile

Full Title

Means for influencing, e.g. improving, the aerodynamic properties of projectiles or missiles; Arrangements on projectiles or missiles for stabilising, steering, range-reducing, range-increasing or fall-retarding (F42B6/00 takes precedence) > Stabilising arrangements > using fins longitudinally-slidable with respect to the projectile or missile