This week is an interview with marine/army sniper Ron. This week is a little different because we were a little short on time but I think that it ended up having a lot of good information in it.
To perform the tall target test you want to set up a target with a perfectible level or "plumb" line with a point on the bottom of the target to aim at. make sure you have a good 100 yard zero and and shoot a group on the bottom of the plumb line. next dial the scope up 20 or 30 MOA or whatever your scope uses. aim for the same spot on the target again and shoot your next group. the next group will be higher on the target. measure the distance between the 2 groups and use this formula to figure out if you have a tracking error in your optic. the formula is - distance in yards to target x amount dialed in MOA x a constant of .01047 = how high the bullets should have hit. - for example when i set up the target was 112 yards away and I dialed 30 MOA so it would look like this 112x30x.01047=35.1792 that's how far the impact should have hit. My bullets hit 35.25 high so I will not add a correction to my ballistic tables.
The other thing that the tall target test will tell you is if your scope is mounted with a cant because the bullets will walk left or right if the optic isn't straight and that will cause your wind calls to off and will make shooting at long ranges very difficult.