Originally Posted by Augustus
I hate to be the bearer of bad news but I just played with the ballistic program a little and it appears that a 308 loaded to send a 175 SMK at 2720 fps and zeroed at 100 yds with the scope 1 in above the bore would be about 1.5 in low at 150 yd. If the scope were 4 in. above the bore the round would hit dead on at 150 yd. Also you could change your sight picture from top to bottom of the scope and not create the error you are talking about. You better shoot her again and see where she goes. When you start talking about shimming scope rings it almost gives me the hives.
Try running your program again using 2.25" center of bore to center of objective.
The scope is 1/2 between top of barrel and bottom of bell, add another 1/2" for center of bore to outside of barrel and divide 50mm by 2 which will give you just over 1.0" added up will be very close and likely just over 2.25" center of bore to center of objective lens, as the barrel is certainly closer to 1.2" on diameter.
This will alter your equation a fair bit.