I agree w/ Longrifle1000. Take the bolt out and actually bore site it. Its free and it works better than you would expect. I recently switched scopes for my .30-06 and sighted in, in just this manner. When I hit the range I was 1/2" low at 25yds, bang on w/horizontal. 1 click and I was dead on at 100yds. I learned this when I was in the artillery shooting 105mm howitzers, in the CDN armed forces.