Help understand red Dot targeting

[Angry_Mammoth]

Hello all, I'm really confused about something and I'm hoping someone can explain I'm a way I can understand.

I'm looking to get a red Dot for my new ar. I've never used one before. I was looking at the EOtech website and they have a pic of targeting with it. It shows the center Dot is zeroed for 50 yards. But to shoot 7 yards you use the bottom mark. This is where I'm confused. Wouldn't that raise the barrel and shoot higher? I'll try and post a pic of the circle from the website.

In my mind this is how it works. If I'm hunting with a regular scope I have it zeroed at 200 yards. If the deer is 300 I use a bottom mark raising the barrel and shooting further. If the deer is 100 I use a upper mark lowering the barrel and shooting closer. Is that not how it works for red dots?

I'm trying to wrap my head around how using a lower mark for closer works. I think I'm just missing something.

Thanks in advance for any help or clarification you can offer.

Sent from my SM-G955U using Tapatalk

 

[BillM]

The center of the sight to the center of the barrel distance is quite a bit on a AR. The bullet will strike LOW at close range---so you have to raise the gun to hit center target.

All guns do it. My .308 sighted in at 200 yds will impact 1.7" low at 100. I have to "raise the rifle" almost 2 MOA to hit center at 100 yds.

Welcome to the forum.

 

[ballardw]

I might think that anything I have to shoot at 7 yards is likely moving, probably in an unfriendly direction, and getting the target inside the ring at all will suffice.

 

[Sharkbite]

In my mind this is how it works. If I'm hunting with a regular scope I have it zeroed at 200 yards. If the deer is 300 I use a bottom mark raising the barrel and shooting further. If the deer is 100 I use a upper mark lowering the barrel and shooting closer. Is that not how it works for red dots?

Thats not how it works.
Think about a football thrown at a distant receiver. The ball makes an arc. Your bullet does the same.
It starts off below your line of sight (LOS) thru the scope or sights. The arc crosses that LOS at 2 distances. With an AR zeroed at 200 yards it first crosses on the upward portion of that arc at about 50. It continues its arc and falls back thru that LOS at the 200yard zero.

So, at any point short of 50, it is still BELOW your LOS. Between 50 and 200 it is ABOVE the LOS and after 200 it will be BELOW your LOS until in hits the earth

So, at a given distance you may need to hold OVER or hold UNDER to get a precise hit. The good news if so self-defense type shooting (not bullseye target type stuff) just put the dot where you want to hit (out to about 250ish) and go.

Hold overs/unders only play a part if you need a precision hit at a distance other the. Your zero. Head shots at 7, hold high...head shot at 100, hold a little low. Center body at 350, hold high.

 

[Unclenick]

Angry Mammoth,

Welcome to the forum. Please head on over here and introduce yourself.

Sharkbite gave a good explanation. A slightly different way to look at it is that the trajectory is divided into three segments by the trajectory arc's rising and falling crossover points with the LOS. For exact vertical POI, at the crossings themselves, you aim right on. At the two end segments, you have to aim high (or use a low spot in your sight reticule), and in the middle segment, you do the opposite to aim low.

 

[reynolds357]

The center of the sight to the center of the barrel distance is quite a bit on a AR. The bullet will strike LOW at close range---so you have to raise the gun to hit center target.

All guns do it. My .308 sighted in at 200 yds will impact 1.7" low at 100. I have to "raise the rifle" almost 2 MOA to hit center at 100 yds.

Welcome to the forum.

How in the world is your rifle set up? 2" high at 100 is usually 200 zero on a 0 cant set up. 25 yd zero is usually 200 yd zero.