I once saw a guy show up in camp bragging about how well he shot. That afternoon we went out to the range to check for zero, and he was all over the place. He just couldn't get the darn thing to respond to the scope adjustments he was making. The P.H. took a look at his rifle and started rolling around on the ground laughing. The scope was mounted 90 degrees off, so when he thought he was changing the windage, he was adding or subtracting elevation and vise versa.