I'll either use a laser bore sighter or if possible take and look down the bore and roughly alighn the scope reticle with a object( rock,piece of paper, etc.) I typically use a clean 3x3 target face (brown wrapping paper bought in a roll) and will fire one shot at a center aiming point. Note where the bullet struck. This will take some type of holding device, I use a rear bag and a front rest.... place the scope back on your aiming point and adjust the reticle to the bullet hole without moving the firearm. Depending on how much you move the firearm doing this will dictate how close you will be to having it shoot dead on. Depending on your skill level, you may have to shoot more shots to fine tune but it shouldnt take more than 2-3 shots total to get it dialed in. It might sound hard but is easy to do. I can never understand how someone can take a 15-20 rounds to sight in.