When it comes to properly zeroing in your AR-15 rifle, there are many schools of thought on the proper way to do it. Personally, because of the help and information I received from from Mr. McQuay from M2Tactical, I will always zero my AR-15 rifles for 50 yards. Please allow me to explain why.
In the video linked above, you will discover why a 50 yard zero for the AR-15 style rifle is my favorite way to zero. With my set up, I have a 1:7 twist ratio barrel and for a sight I have an Aimpoint PRO
with a 2MOA dot. I had originally zeroed my rifle for 100 yards. When I placed my red dot on the bullseye at 100 yards, assuming I exercised my marksmanship fundamentals well, I would hit it. However, with that zero, when tried to shoot a target at 25 yards, I found my aim was off quite a bit. With self defense in mind, would I want to place the red dot/sights where I want the bullet to go (point of aim = point of impact), and then pull the trigger without thinking about bullet drop and elevation? Definitely. That is why the 50 yard zero is so important for my shooting purposes.
What is bullet drop?
Remember from school that whatever goes up, must come down? Think of that when thinking of bullet drop. When you pull the trigger on your AR-15, the bullet leaves the barrel traveling very fast, soaring through the air and falling, that is, losing elevation, because of gravity. Point of aim is a straight line from your eye to the target, but the bullet travels slightly above and below that line depending on distance. This is why a 50 yard zero is simple. Take a look at the picture M2Tactical provided me for a better visual on bullet drop, point of aim, and point of impact.
Why zero for 50 yards?
There is one key reason I choose to zero at 50 yards, and that is simplicity. Because of bullet drop, a 50 yard zero allows one to place their point of aim on center of mass from 25 out to 300 yards and the bullet will strike the target. So, in other words, I can place my red dot (or point of aim) on my target from 25 yards all the way out to 300 yards and I will hit my target (again, assuming I exercise good marksmanship fundamentals) with only a spread of roughly six inches from point of aim to point of impact. This allows the shooter to take a lot of guess work out of where to aim. Place the red dot on the target, pull the trigger, and you will hit it.
My Iron sights (YMH folding) came zeroed at 50 yards. It seemed to work well, so I have just stuck with that with every thing I have stuck on it. It is nice to know why that is.
That’s a good point, and is explained really well in the video.
This concept is called point blank range, and is well known among hunters.
You can fine tune your zero, calculating with a ballistic software the exact zero range that allows you to stay in the vital zone for the maximum distance possible. You probably wont obtain a standard zero range like 25, 50 or 100y. However, if you can’t zero at that specific range, you can see what is the amount of drop at your favorite zero range (for me it is 100m for scoped rifle and 50m for carbines), and adjust your sights so that aiming dead center your point of impact is lower (or higher) of that amount.
Making a rapid calculation with JBM ballistics, for a 55gr FMJBT at 3100fps (16″ barrel) I obtain for a vital zone of 10″:
Maximum Point Blank Range = 353y (the farthest distance at which you can hit the vital zone aiming dead center).
Range of Maximum Height = 177y (the distance at which, aiming dead center, the point of impact is on the top of the vital zone).
Max PBR Zero Range = 304y (is the range at which you have to zero tho optain the Max Point Blank Range. For casuality, it is very close to 300y)
Drop at 50y = +1,1″ or +2.1 MOA (the plus sign means that the drop is above line of sight)
This means that if you want to zero at 50y, you have to adjust the sights so that aiming dead center, the bullets still hit 1.1″ high. A target like the one shown in the vid will help in this process 😉
would this work with a Cross hair scope too?
If i am using a 3-9 X40 scope. I am thinking that if i set it to the fully un-zoomed setting that I should be able to zero that the same way? If not what would you suggest?
This aiming/zeroing system will work with any optic on any rifle … as long as the sights are mounted at the same height as an AR-15, and firing the same ammo at the same velocity.
This is a great link that will help you understand some of the dynamics. Raising or lowering the sights will change your “height over bore” aka “sight offset”. Anything that changes your trajectory, like a change in velocity, will also change the overall effect. http://arma-dynamics.com/zero-considerations.html
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