Yea assuming muzzle velocity 1000m/s and 3kg projectile weight and 6000kg aircraft weight, conservation of momentum would put the slowdown at 0.5m/s, hardly not

Yea assuming muzzle velocity 1000m/s and 3kg projectile weight and 6000kg aircraft weight, conservation of momentum would put the slowdown at 0.5m/s, hardly noticable at cruising speed I think. Though the jerk would most likely be noticable.