I have read the typical stuff that gets repeated on the internet, which says, adjust your parallax for long range or you'll miss.
But, I have read and listened to several optics experts who have disabused me of the notion. The technical aspect of optics is way more than I fully understand and more than I need to understand. But, assuming what they say about the math and the way light bends and passes through the lenses in the scope, it is pretty simple.
To avoid parallax and NEVER have a problem, just learn to center your eye in the scope. Learn what it looks like and make it repeatable. I like to set my eye relief so that I can see a little ring of scope around the lens. I then have a reference to center my eye in the scope.
IF YOU CENTER YOUR EYE EVEN CLOSE YOU WILL NEVER MISS AN ANIMAL BECAUSE OF PARALLAX.
To understand why even getting close to centering your eye will eliminate misses from parallax error, I'll just explain what the maximum error would be if you used the absolute worst sight picture ever. And, I don't think anyone would even think about shooting in such a bad position. If you would, you need much more help on marksmanship before even shooting at 100 yards...
To get maximum parallax error, you need to be looking through the scope at the maximum angle. You would have so much scope shadow that you can barely see the crosshair in a tiny sliver of visible light. I don't think anyone shoots with that much scope shadow. It can only happen if you are looking through the scope at a severe angle and your eye is looking through the outer edge of the lens. I will repeat that no competent rifleman does that.
Now, for shooting for groups at 100, parallax can be an issue that opens up your groups because you are measuring them and small errors are visible. So, take the time to focus and get perfectly behind the rifle so you can't blame parallax.
Just to give you an idea of where parallax matters to a hunter, lets look at types of error assuming you have the worst possible sight picture, a sliver of light and the rest shadow.
Setting parallax really close and shooting far AND you have the worst possible scope shadow. For instance, if you have parallax set for 100 yards, and shoot at 200 yards. The absolute MOST you can miss is 25mm (1.1 inch) with a 50mm objective scope. At 300 yards the most you can miss is about 2.2 inches, and at 400 the most you can miss is about 3.3 inches. The pattern continues until at 1000 it is 10 inches. But, remember, you have to literally be looking through the tiniest sliver with your eye looking through the lens as far from the center as you can. If you are able to consistently get your eye centered in your scope with minimal scope shadow, parallax won't make you miss.
Setting parallax on infinity AND having the worst possible scope shadow. Because of the mechanics of the scope and the angles involved, at 300 yards, the error is less than one inch and the error decreases slowly the further you go.
Setting parallax on 300 and shooting at 400 AND having the worst possible scope shadow. Here, we are back to less than one inch of error only if you have terrible position.
So, I'll summarize the parallax in three parts.
First, learn to center your eye in the scope. Get your rifle set up and learn to put your head in the same place every time. You will never have a parallax error and you will have other benefits that follow consistency. You won't ever need to adjust parallax to make a perfect shot.
Second, just use the parallax as a focus knob, and get the image in focus. It will be close enough that it won't matter for any hunting application.
Third, put the parallax somewhere between 400 and infinity and the maximum possible error is so small that there is no way parallax will cause a miss whether it is a quick shot inside 100 yards or a time crunched shot inside 600.
But, I have read and listened to several optics experts who have disabused me of the notion. The technical aspect of optics is way more than I fully understand and more than I need to understand. But, assuming what they say about the math and the way light bends and passes through the lenses in the scope, it is pretty simple.
To avoid parallax and NEVER have a problem, just learn to center your eye in the scope. Learn what it looks like and make it repeatable. I like to set my eye relief so that I can see a little ring of scope around the lens. I then have a reference to center my eye in the scope.
IF YOU CENTER YOUR EYE EVEN CLOSE YOU WILL NEVER MISS AN ANIMAL BECAUSE OF PARALLAX.
To understand why even getting close to centering your eye will eliminate misses from parallax error, I'll just explain what the maximum error would be if you used the absolute worst sight picture ever. And, I don't think anyone would even think about shooting in such a bad position. If you would, you need much more help on marksmanship before even shooting at 100 yards...
To get maximum parallax error, you need to be looking through the scope at the maximum angle. You would have so much scope shadow that you can barely see the crosshair in a tiny sliver of visible light. I don't think anyone shoots with that much scope shadow. It can only happen if you are looking through the scope at a severe angle and your eye is looking through the outer edge of the lens. I will repeat that no competent rifleman does that.
Now, for shooting for groups at 100, parallax can be an issue that opens up your groups because you are measuring them and small errors are visible. So, take the time to focus and get perfectly behind the rifle so you can't blame parallax.
Just to give you an idea of where parallax matters to a hunter, lets look at types of error assuming you have the worst possible sight picture, a sliver of light and the rest shadow.
Setting parallax really close and shooting far AND you have the worst possible scope shadow. For instance, if you have parallax set for 100 yards, and shoot at 200 yards. The absolute MOST you can miss is 25mm (1.1 inch) with a 50mm objective scope. At 300 yards the most you can miss is about 2.2 inches, and at 400 the most you can miss is about 3.3 inches. The pattern continues until at 1000 it is 10 inches. But, remember, you have to literally be looking through the tiniest sliver with your eye looking through the lens as far from the center as you can. If you are able to consistently get your eye centered in your scope with minimal scope shadow, parallax won't make you miss.
Setting parallax on infinity AND having the worst possible scope shadow. Because of the mechanics of the scope and the angles involved, at 300 yards, the error is less than one inch and the error decreases slowly the further you go.
Setting parallax on 300 and shooting at 400 AND having the worst possible scope shadow. Here, we are back to less than one inch of error only if you have terrible position.
So, I'll summarize the parallax in three parts.
First, learn to center your eye in the scope. Get your rifle set up and learn to put your head in the same place every time. You will never have a parallax error and you will have other benefits that follow consistency. You won't ever need to adjust parallax to make a perfect shot.
Second, just use the parallax as a focus knob, and get the image in focus. It will be close enough that it won't matter for any hunting application.
Third, put the parallax somewhere between 400 and infinity and the maximum possible error is so small that there is no way parallax will cause a miss whether it is a quick shot inside 100 yards or a time crunched shot inside 600.
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