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Posted: 7/22/2010 6:45:29 PM EDT
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Question about scope adjustment
I have a Bushnell Trophy 1-4x24 mm scope #731424M in a 30 mm tube. I have bore sighted it at 25 yards. When I shot my group at 25 yds it was high and to the right of Point of Aim which was at the target center. When adjusting the windage and elevation, do I 1.Adjust the elevevation up and the windage right according to the turret arrows , (Trying to put the scope reticle at the center of the group.) or, 2.Adjust the elevation down and windage left according to the turret arrows. (trying to put the POI to the POA which was at the center of the target. The opposite of 1. Abovr 3.Please explain the adjustment principles for this scope. Please include some illustrations (drawings) if possible. Am I adjusting the POA to the POI, or am I adjusting the POI to the target center POA? I stay confused on this principle and seem to receive an equal amount of advice for both procedures. The manufacturers instructions are not always thorough and clear on this. Does this vary with different scope manufacturers or is there an industry standard? |
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Now you made me think!
What I do is shoot a group, then with the gun securely in the rest, with the crosshairs on the point of aim, turn the dials until the crosshairs are centered on the group. If the shot is way off, do it like this on the first shot, and save a lot of ammo. UP (usually clockwise), means moving the POI up, so if you're shooting high, you need to turn counter clockwise to bring the group down. |
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Quoted: Question about scope adjustment I have a Bushnell Trophy 1-4x24 mm scope #731424M in a 30 mm tube. I have bore sighted it at 25 yards. When I shot my group at 25 yds it was high and to the right of Point of Aim which was at the target center. When adjusting the windage and elevation, do I 1.Adjust the elevevation up and the windage right according to the turret arrows , (Trying to put the scope reticle at the center of the group.) or, 2.Adjust the elevation down and windage left according to the turret arrows. (trying to put the POI to the POA which was at the center of the target. The opposite of 1. Abovr 3.Please explain the adjustment principles for this scope. Please include some illustrations (drawings) if possible. Am I adjusting the POA to the POI, or am I adjusting the POI to the target center POA? I stay confused on this principle and seem to receive an equal amount of advice for both procedures. The manufacturers instructions are not always thorough and clear on this. Does this vary with different scope manufacturers or is there an industry standard? It would be better if you zero'd your system at 100 yards or near 100 yards. This scope is focused there and therefore parallax error is minimal. Beyond 100 yards parallax error increases, but not a whole lot to be worried about. Normally, most bullets have a greater variance in their ballistic paths than the amount of parallax error in a typical scope. However, at 25 yards, this scope will have around 3 inches of error caused by parallax. You're going to play "chase the bullet hole" if you zero at 25 yards and then move out to greater distances. It's better to zero at 100 yards then compensate (if you think you need to) for 25 yards. As for adjusting a scope or any sight system for that matter, don't over analyze it. You're shooting a group to determine the average location of a Point of Impact. Then think of it as moving this group to the center of the target. I understand what you're thinking about in the above choices 1 and 2. Normally, the instructions for telescopic sights normally have you move the POIs to the center of the target while reflexive red dot sights will have you tighten up the group and be consistent in hits. I'm not sure what adjustment principle means, so here's a description of the insides. You have an erector tube with a set of lenses in it. The principle job of the erector tube is to invert the image. (This is called an non-Galilean instrument.) In variable powered scopes, one set of lenses, or one lens depending on the construction, is movable to change the focal length. This is what you're doing when you move the power selector ring. The end of the erector tube closest to the eye piece is fixed in position. The other end is movable. Therefore the erector tube has a pivot point. When you turn the adjusting screws, you're pushing the erector tube one way against a spring or you letting the spring push the erector tube against the screws (depending on which way you're turning the screws.) This mechanical set up is what is sometimes referred to as the "gimbal." IMHO, the most important thing to remember is that the bullet will go in the direction the muzzle is pointed as the bullet clears the muzzle. The basics of shooting are important. Being consistent with your body, breathing and mental focus are huge determiners in where the bullet ends up. Consistency equals accuracy. Hope this helps. |
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Quoted:
Question about scope adjustment 1.Adjust the elevevation up and the windage right according to the turret arrows , (Trying to put the scope reticle at the center of the group.) or, This way works but requires a solid rest for the gun to ensure the gun doesn't move while adjusting the scope. This could be as simple as firing one shot then adjusting the POA to the POI. This way, as you described, you are moving the crosshairs on the scope to coincide with the impact point of the bullet. 2.Adjust the elevation down and windage left according to the turret arrows. (trying to put the POI to the POA which was at the center of the target. The opposite of 1. Abovr This is the more traditional way of adjusting a scope since most people do not have a sold rest that holds the gun immobile during scope adjustment. The turret knobs are marked with a "U" or "D" for elevation and "L" or "R" for windage. You adjust the turrets in the direction you desire the POI to move. In your case you would want to move the elevation knob "Down" to move the impact point closer to the aim point. You would move the windage knob "Left" to move impact point closer to the aim point. Both ways work but you're using a different technique for each setting. And as some suggested it would be better to make adjustments further out than 25 with 100 being more ideal for an optical scope. If you don't have a boresight device then get on paper at 50 then move to 100. |
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