The Firing Line Forums - View Single Post

stepmac · January 27, 2013, 04:32 PM

Here is the SIGHT ADJUSTMENT RULE:

Move the rear sight in the direction you want the bullet to move.

Move the front sight in the opposite direction you want the bullet to move.

So, when adjusting the rear sight, if you want the bullet to go left turn the sight adjustment so that the rear sight moves left.

If, however you are shooting a rifle (or pistol) that drifts the front sight to adjust bullet impact and you want the bullet to move to the left you drift the front sight TO THE RIGHT.

So windage adustment using the rear or front sights are opposite from one another.

Same goes for elevation. If you want the bullet to rise, move the rear sight up. If you are adjusting your front sight; if you want the bullet to go up you file down the front sight.

Got that? You have to think about it, because it's easy to forget.

Concerning elevation: The relationship between line of sight and bullet tragectory is something you have to study, because when the bullet leaves the muzzle it is below the line of sight, then it rises to cross the line of sight, then it falls back down to it and then keeps going below.

So, The bullet will cross the line of sight twice. Once going up and the other coming down. Therefore the rifle will appear to be perfectly sighted in at two places, one close and the other far. Reloading manuals will help you with this trajectory stuff.

One more thing. There is something called "drift". The bullet's flight is affected by the spin of the bullet. This has a measurable affect in large caliber guns and slower moving bullets, like the old 45/70 and artillery rounds. It affects small fast bullets too, but since they are in the air less time it is not so noticeable.

Look at an old Trapdoor Springfield Buffington rear sight. You will note that as the rear sight is elevated it also moves to the left. Why? Compensation for drift, of course. The bullet, due to drift moves right. Since we move the rear sight the same direction we want the bullet to move, the rear sight angles left as it rises. The farther the bullet flys the more time drift has to move the bullet, so the affect of drift increases with range and so does the rear sight move farther left as it rises. The rear sight on an Artillery Luger is similar. I think that the 1898 Krag's rear sight has drift compensation too. Drift is significant, I'm told, when firing artillery rounds which makes sense. Unless you are a target shooting you don't need to worry about drift.

Today artillery fire is computerized. It used to be a slip stick computation. They even compensate for the turning of the Earth while the round is on it's way down range. Artillery rounds also go very high. The extreme heigth of an arty round is called it's Max Ord. It is something like 30,000' (I can't recall). Saddam Hussein was making a cannon that could shoot into space and hit Israel! The barrel was planted underground and bolted together like pieces of pipe.

I'll bet there are some arty guys here who know a lot more about cannon fire than I do. It is an interesting science.

January 27, 2013, 04:32 PM	#6
stepmac Member Join Date: January 17, 2013 Posts: 41	Here is the SIGHT ADJUSTMENT RULE: Move the rear sight in the direction you want the bullet to move. Move the front sight in the opposite direction you want the bullet to move. So, when adjusting the rear sight, if you want the bullet to go left turn the sight adjustment so that the rear sight moves left. If, however you are shooting a rifle (or pistol) that drifts the front sight to adjust bullet impact and you want the bullet to move to the left you drift the front sight TO THE RIGHT. So windage adustment using the rear or front sights are opposite from one another. Same goes for elevation. If you want the bullet to rise, move the rear sight up. If you are adjusting your front sight; if you want the bullet to go up you file down the front sight. Got that? You have to think about it, because it's easy to forget. Concerning elevation: The relationship between line of sight and bullet tragectory is something you have to study, because when the bullet leaves the muzzle it is below the line of sight, then it rises to cross the line of sight, then it falls back down to it and then keeps going below. So, The bullet will cross the line of sight twice. Once going up and the other coming down. Therefore the rifle will appear to be perfectly sighted in at two places, one close and the other far. Reloading manuals will help you with this trajectory stuff. One more thing. There is something called "drift". The bullet's flight is affected by the spin of the bullet. This has a measurable affect in large caliber guns and slower moving bullets, like the old 45/70 and artillery rounds. It affects small fast bullets too, but since they are in the air less time it is not so noticeable. Look at an old Trapdoor Springfield Buffington rear sight. You will note that as the rear sight is elevated it also moves to the left. Why? Compensation for drift, of course. The bullet, due to drift moves right. Since we move the rear sight the same direction we want the bullet to move, the rear sight angles left as it rises. The farther the bullet flys the more time drift has to move the bullet, so the affect of drift increases with range and so does the rear sight move farther left as it rises. The rear sight on an Artillery Luger is similar. I think that the 1898 Krag's rear sight has drift compensation too. Drift is significant, I'm told, when firing artillery rounds which makes sense. Unless you are a target shooting you don't need to worry about drift. Today artillery fire is computerized. It used to be a slip stick computation. They even compensate for the turning of the Earth while the round is on it's way down range. Artillery rounds also go very high. The extreme heigth of an arty round is called it's Max Ord. It is something like 30,000' (I can't recall). Saddam Hussein was making a cannon that could shoot into space and hit Israel! The barrel was planted underground and bolted together like pieces of pipe. I'll bet there are some arty guys here who know a lot more about cannon fire than I do. It is an interesting science.