While shooter error is always a possibility, people that shoot inch groups at 100 don't usually throw them around at 150 so I doubt that's a problem, a lot of shooters that usually shot cartridge guns will measure the powder carefully and ram the load down with a bit difference in ramming force there for seating pressure each time. Usually a shooter that's getting an inch group at 100yds will have more trouble with the wind moving the bullet horizontally than with vertical stringing. Also if the sabot did not fit well there would not be any inch groups at a 100yds. Shooting before the gun is cooled off or seating pressure would be the things I would look at first. Lee