I've got an old bsa boresighter. It works with 7 mm caliber. 22 caliber but when I put the 30 caliber insert in it's always way above the top of the grid. Bore sighted a 30-30 with new Burris full field scope and was out of clicks before I could get low enough to get on the grid. That's 4 30 caliber rifles it's done that on. Went to lgs and they had plenty of clicks left and was spot on. Any idea why the 30 caliber does this.