By a box (5 rounds) of several different types of sabot slugs...

Boresight the gun to get it on paper... Set up your paper target (with an aiming point for each type of slug) at a distance of 25-50 yards...

Shoot at least a 3 shot group with each type of slug (do NOT change the scope settings / rifle sights...you are not sighting in here)...look for the size of the groups...this is to figure out which slugs your gun/barrel likes best...

When you figure out which slug that your gun/barrel likes, buy several boxes...try to sight in using the 2 shot method at 25 yards, then adjust your zero to whatever range you determine to be best for your hunting...

If you are using a scope, make sure you have high quality (steel) bases and rings because of the recoil...