Assuming the ammo is identical in every way and the barrel must be fired while inside the slide, the only way to get any kind of accurate group to the point that a flyer can be reasonably isolated, will be with a clamped down pistol, the barrel cleaned before every shot, and then only shot when the barrel is cooled to the same temperature each time. Without this, you are talking about expanding gas that is pushing a high friction projectile down irregular surfaced tighter ID tube with a coefficient of kinetic friction that is changing (getting dirty) with each shot and while the barrel temperature is rapidly changing. Without that level of measure and removal of human influence, technically most every shot is a "flyer" and maybe only one of those in that group of ten is where it should be.