Your question was NOT stupid. If you look at a trajectory chart, you will find the bullet crosses the line of sight twice. Once close to muzzle and again at a longer range. Your 30-30 will cross the first time at about 25 yards with a typical scope mounted in standard, as in low rings. Then crosses again at about 175 yards, dependent on initial muzzle velocity. If you are using iron sights, the first cross is at about 20 feet and the second is about 125 yards. If your hold at 25 yards was good, you will only be off maybe an inch on the side to side at 100 yards. That is minus wind drift, which only you at the time of the shot will know. My father sighted in his 38-55 at kitchen door to the woodshed every year, about 75 feet. Sometimes he would check by shooting at a "little rock" across the road to the orchard, maybe 100 yards. He killed more white tails than most anyone, and at that time deer were scarce in WV.
