If you are shooting an Auto-loader it's more than likely shooter error. If you are shooting a Revolver it could be you as well, but I would temporarily mark the Charge Holes in the Cylinder so that you can keep accurate track of which rounds are flyers. If the flyers are always from the same Charge Hole then you probably have an issue with the gun itself. If all the shots from several Cylinders full are all tightly grouped, then it's probably shooter error but have a known accomplished shooter try it and see how he groups.