You need to know where your lands are, that way you have a starting point with your handloads. Some guys like to KISS the lands and others like to back the bullet off by about .020". That way, you know the ammo will reliably chamber in your rifle. Furthermore, You don't want the bullet to be jammed into the lands or you will have trouble chambering the round. Make sure you are setting your dies up properly and know where your lands are and half the battle will be won.
