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So after a brief discussion that turned into an interesting argument with a buddy of mine, I figured I'd share this here.
My friend wanted to spend a large amount of money on an expensive laser sighting tool. Site Lite. Something like $200 dollars for the thing.
I told him not to buy it and that he could sight in his rifle at any distance with a little math and either a ruler or a set of calipers.
He did what I said, then proceeded to get even more angry when I was right.
So the simple no ammo used version of how to sight in any optic goes like this.
First off, there is one disclaimer. Your gear must be of good quality. IE if you buy a cheap base that is machined poorly and is not correctly to spec, this isn't going to work. Same for cheap scopes, AR15 uppers, barrels, ammo and the like.
Ok so let's talk numbers.
What do you know.
Minute of angle, well most everyone knows minute of angle. It's roughly an inch at one hundred yards. Yes, sort of. Really, MOA is an angle. In mathematical terms, it is 1/60 of a degree or 0.0167 degrees. A straight line drawn to 100 yards with a second straight line drawn at 0.0167 degrees will be 1.047" above the other.
Ok. We know MOA. Now we need to know your gun, well mostly your ammo, but kind of your gun. You need to know your velocity. You can go off the ammo manufacturers tested velocity and not fire a round or five to get an average velocity for your choice ammo using a chrono. Otherwise, using the manufacturers velocity you know your bullets ballistics and can calculate its drop. However, to note, most centerfire cartridges at above 2500 feet per second tend to have little to no drop to 100 yards. So with that known, you can state the bullet leaving the barrel will travel in a straight line to 100 yards, again this can be altered by quality. However, most modern day barrel manufacturers are capable of making a barrel that can produce sub MOA results. If your manufacturer claims this, I'd say your safe.
Next you need to know your optics bore height. You can go super calculated and measure everything, the thickness of your barrel, the height of your rings, the thickness of your receiver, etc. The more accurate this measurement the better your results. To put this simply, we are going to say your scopes bore height is two inches. In other words, the center of your optic is two inches above the center of your bore. This is were quality comes in, some scopes are created differently then others, some may not even be capable of being centered. To center your optic, adjust both your elevation and windage in one direction count the number of clicks till you hit the absolute other side. Divide buy two. Adjust back till centered.
So now the math, well, with the above scenario things are extremely easy. Your scope is 2" above your bore line. If you were to fire a round, so long as the ammo and barrel aren't of horrible quality, your round should impact 2" below your point of aim if your ammo has ballistics with zero drop at 100 yards. With a scope that has adjustments in MOA, you would need to adjust up 2 minutes, or 8 clicks if your adjustments are 1/4 MOA.
Want to zero a red dot for your pistol at 7 yards. Same thing just use math. At 7 yards MOAwould equate to 0.073". Measure your bore height and divide the height by 0.073" and you'll get the number of minutes you need to adjust.
Thought I'd share!
Edit: See post 27
My friend wanted to spend a large amount of money on an expensive laser sighting tool. Site Lite. Something like $200 dollars for the thing.
I told him not to buy it and that he could sight in his rifle at any distance with a little math and either a ruler or a set of calipers.
He did what I said, then proceeded to get even more angry when I was right.
So the simple no ammo used version of how to sight in any optic goes like this.
First off, there is one disclaimer. Your gear must be of good quality. IE if you buy a cheap base that is machined poorly and is not correctly to spec, this isn't going to work. Same for cheap scopes, AR15 uppers, barrels, ammo and the like.
Ok so let's talk numbers.
What do you know.
Minute of angle, well most everyone knows minute of angle. It's roughly an inch at one hundred yards. Yes, sort of. Really, MOA is an angle. In mathematical terms, it is 1/60 of a degree or 0.0167 degrees. A straight line drawn to 100 yards with a second straight line drawn at 0.0167 degrees will be 1.047" above the other.
Ok. We know MOA. Now we need to know your gun, well mostly your ammo, but kind of your gun. You need to know your velocity. You can go off the ammo manufacturers tested velocity and not fire a round or five to get an average velocity for your choice ammo using a chrono. Otherwise, using the manufacturers velocity you know your bullets ballistics and can calculate its drop. However, to note, most centerfire cartridges at above 2500 feet per second tend to have little to no drop to 100 yards. So with that known, you can state the bullet leaving the barrel will travel in a straight line to 100 yards, again this can be altered by quality. However, most modern day barrel manufacturers are capable of making a barrel that can produce sub MOA results. If your manufacturer claims this, I'd say your safe.
Next you need to know your optics bore height. You can go super calculated and measure everything, the thickness of your barrel, the height of your rings, the thickness of your receiver, etc. The more accurate this measurement the better your results. To put this simply, we are going to say your scopes bore height is two inches. In other words, the center of your optic is two inches above the center of your bore. This is were quality comes in, some scopes are created differently then others, some may not even be capable of being centered. To center your optic, adjust both your elevation and windage in one direction count the number of clicks till you hit the absolute other side. Divide buy two. Adjust back till centered.
So now the math, well, with the above scenario things are extremely easy. Your scope is 2" above your bore line. If you were to fire a round, so long as the ammo and barrel aren't of horrible quality, your round should impact 2" below your point of aim if your ammo has ballistics with zero drop at 100 yards. With a scope that has adjustments in MOA, you would need to adjust up 2 minutes, or 8 clicks if your adjustments are 1/4 MOA.
Want to zero a red dot for your pistol at 7 yards. Same thing just use math. At 7 yards MOAwould equate to 0.073". Measure your bore height and divide the height by 0.073" and you'll get the number of minutes you need to adjust.
Thought I'd share!
Edit: See post 27
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