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Q:
How do you correctly determine sight height for a scope, and exactly how important is this when calculating a true zero?
Question by Killswitch. Uploaded on October 27, 2009
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Answers (3)
The lower the better. As long as the objective is not touching the barrel you're good. On a rifle I used to have I actually had to cut a section out of my scope cover so I could put it on it was so close. You'll bve able to shoot more accurately if you have a better cheek weld which is what a lower mount will help you achieve.
That is why I don't like a large diameter abjective. Mine is only 33 mm and it is fantastic. I was able to use Extra Low rings.
Measure from the center of the bore up to the center of the scope tube or lens. This is only needed if using a ballistics program or chart to determine point of impact.
Importance? Depends on how close to 100 yard zero you want to theoretically be. You should fine tune the scope and check at various yardages anyway.
Let's say your scope is at 1.5" ... for a typical factory 270WSM you need to sight at -0.8" at 25 yards to zero at 100 yards. For a scope at 2" you need to sight in at -1.2" at 25 yards to zero at 100 yards.
All bullets probably won't go through the same hole, so you are averaging the impact points. Some bullets also don't stabilize at short ranges so impacts at 100 yards might not be where calculated. Same with longer ranges. Not all guns will shoot bullets at the same velocity. So ... still have to check targets at various ranges and fine tune.
+s for both above. Go as low as you possibly can for hunting. Not such an issue for calculating trajectory as it is for missing your target. Try canting your rifle about 10 degrees and shooting with a high scope... you will notice that the bullet hits several inches to one side at 200 yards. The effect of canting your rifle is greatly magnified with high mounts. Still OK but just be aware and pay special attention to keeping the scope directly above the barrel... especially if you are shooting out to 300-400 yards.
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Measure from the center of the bore up to the center of the scope tube or lens. This is only needed if using a ballistics program or chart to determine point of impact.
Importance? Depends on how close to 100 yard zero you want to theoretically be. You should fine tune the scope and check at various yardages anyway.
Let's say your scope is at 1.5" ... for a typical factory 270WSM you need to sight at -0.8" at 25 yards to zero at 100 yards. For a scope at 2" you need to sight in at -1.2" at 25 yards to zero at 100 yards.
All bullets probably won't go through the same hole, so you are averaging the impact points. Some bullets also don't stabilize at short ranges so impacts at 100 yards might not be where calculated. Same with longer ranges. Not all guns will shoot bullets at the same velocity. So ... still have to check targets at various ranges and fine tune.
The lower the better. As long as the objective is not touching the barrel you're good. On a rifle I used to have I actually had to cut a section out of my scope cover so I could put it on it was so close. You'll bve able to shoot more accurately if you have a better cheek weld which is what a lower mount will help you achieve.
That is why I don't like a large diameter abjective. Mine is only 33 mm and it is fantastic. I was able to use Extra Low rings.
+s for both above. Go as low as you possibly can for hunting. Not such an issue for calculating trajectory as it is for missing your target. Try canting your rifle about 10 degrees and shooting with a high scope... you will notice that the bullet hits several inches to one side at 200 yards. The effect of canting your rifle is greatly magnified with high mounts. Still OK but just be aware and pay special attention to keeping the scope directly above the barrel... especially if you are shooting out to 300-400 yards.
Post an Answer