MOA bullet drop question

[longtalltechsan]

On the Millett DMS the donut reticle is 12moa on the outside and 10moa inside. If I have it sighted in at 100 yards, but am aiming at a target at 50 yards bullet impact should be 2.5" +/- lower than 100 yard bullet impact, correct?

And if the above is true, and the inside diameter of the donut is 10moa, then at 50 yards it is 5 moa and half the circle would be 2.5moa, correct?

Basically if I am sighted in at 100 yards, but want to shoot at 50 yards, based on bullet trajectory, I could put the bottom of the inside of the donut on my target and be right on. Is this correct?

ETA: In my twisted mind this makes sense. I guess another way to ask it would be if I am sighted in at 100 yards but am aiming at something 50 yards out, what part of the reticle do I put on my target?

Oh, and this in on a 5.56 AR typically using 55grn ammo.

[scalce]

Sounds good to me.

I guess I can test the theory when I go to resight in my DMS.

I use this gun for range fun and 3 gun so I am trying to decide if 50 yards or 100 yards makes more sense.

[EricCartmann]

Bullet will only be about 3/4th of an inch lower between 100 and 50 yards.. It really depends on your scope/sight height. I assume it is 2.5" over the bore, in this case, it will be 2.5" low at 0 yards, about .75" low at 50 yards, and dead on at 100 yards (the distance you zeroed at).

You got the right idea about MOA, but MOA does not change at distance. 10 MOA is 10 MOA and always stays 10 MOA. At 100 yards 10 MOA is roughly 10", at 200 yards it is rougly 20", at 300 yards it is rougly 30"... at 50 yards 10 MOA is roughly 5". So you got the right idea, just the terminology wrong.

If you zero a .223 at 100 yards. I would just aim center mass from 0-200 yards. The POA/POI shift between 50 and 100 yards is only 3/4th of an inch so I would not even bother trying to adjust for that distance. I myself like to zero at 100 since I don't plan to use my AR for more than 300 yards. For a 100 yard zero, expect to be dead on at 100 yard, 2" too low at 200, 10" too low at 300... at 600 yards I will be a about the height of a man too low (70").

Some people like to zero at 25 yards as this is better for distance. If you zero at 25, expect to be 6" too high at 100 yards, 9" too high at 200 yards, 10" too high at 300 yards, dead on at 400 yards, and 10" too low at 500 yards.

[longtalltechsan]

Thanks Cartman. I know MOA doesn't change based on shooting distance. After reading what I typed I didn't say it correctly or didn't really clarify part of what I was saying.

Thanks a bunch for the info. Hopefully I'll get to zero it this weekend and find out different impacts based on distances and aim.

[Tomcat088]

I have never held a DMS scope before, but I wanted to mention one thing. You need to know whether your reticle is in the first focal plane (FFP) or the second focal plane (SFP) before you start using your reticle to strictly judge distance and hold over. A second focal plane reticle will stay exactly the same size as you zoom through the powers of the scope, a first focal plane reticle will seem to get larger or smaller as you zoom through the powers. Other Millett scopes have SFP reticles, but I am not sure about the reticle on the DMS. I called millet and spoke with Mike, he said that the information wasn’t in the computer and he hadn’t been able to get a sample in their store, so he wasn’t sure. He did say that all of their other rifle scopes are second focal plane reticles. This is important to know because if the reticle is in the second focal plane, it will only be 1MOA, 10MOA etc at only one power setting. You can still judge distance with the other settings, but you have to account for what power you are on as to how many MOA everything covers. From the information that I see on their online instructions for the rifle scope, it appears to be a second focal plane reticle that the dot is 1moa at 4x. This means that if you were on 2x, the dot actually covers roughly 2moa, the inside of the donut covers roughly 20moa, and the outside covers around 24moa. The documentation says that at 100 yards the outside of the donut spaces 51.6” and the inside of the donut spaces 43”.

What this breaks down to is that you could also crunch some numbers and figure out what magnification would dictate how many inches that your bullet drops from the center of the reticle and use that. Remember that not all 55 grain bullets drop the same amount. This will depend on your muzzle velocity, weight of the bullet, length of your barrel; at longer ranges distance shooters take into account temperature, barometric pressure and other variables. Just thought that I would toss that out there, so that you knew that the reticle is ONLY ACCURATELY 1moa, 10moa, 12moa at 4x.

[EricCartmann]

That's a good point about FFP and SFP. I too believe the Millet to be SFP.

According to the ammo oracle and from what I have found, For 300 yards or less there the drop is really negligible between M855 (62gr) and M193 (55gr). Same thing goes for muzzle velocity. Between 16" and 20" there is only about 100-150 fps difference. For 300 yards or less this also will not make much of a difference. Military surplus ammo is only about 4-5 MOA anyways.

Now if you are building a precision or varmint AR where accuracy and distance matters then that is another story.

[longtalltechsan]

Originally Posted by Tomcat088

I have never held a DMS scope before, but I wanted to mention one thing. You need to know whether your reticle is in the first focal plane (FFP) or the second focal plane (SFP) before you start using your reticle to strictly judge distance and hold over. A second focal plane reticle will stay exactly the same size as you zoom through the powers of the scope, a first focal plane reticle will seem to get larger or smaller as you zoom through the powers. Other Millett scopes have SFP reticles, but I am not sure about the reticle on the DMS. I called millet and spoke with Mike, he said that the information wasn’t in the computer and he hadn’t been able to get a sample in their store, so he wasn’t sure. He did say that all of their other rifle scopes are second focal plane reticles. This is important to know because if the reticle is in the second focal plane, it will only be 1MOA, 10MOA etc at only one power setting. You can still judge distance with the other settings, but you have to account for what power you are on as to how many MOA everything covers. From the information that I see on their online instructions for the rifle scope, it appears to be a second focal plane reticle that the dot is 1moa at 4x. This means that if you were on 2x, the dot actually covers roughly 2moa, the inside of the donut covers roughly 20moa, and the outside covers around 24moa. The documentation says that at 100 yards the outside of the donut spaces 51.6” and the inside of the donut spaces 43”.

What this breaks down to is that you could also crunch some numbers and figure out what magnification would dictate how many inches that your bullet drops from the center of the reticle and use that. Remember that not all 55 grain bullets drop the same amount. This will depend on your muzzle velocity, weight of the bullet, length of your barrel; at longer ranges distance shooters take into account temperature, barometric pressure and other variables. Just thought that I would toss that out there, so that you knew that the reticle is ONLY ACCURATELY 1moa, 10moa, 12moa at 4x.

Thanks for that info Tomcat.

How is Lubbock theses days? I lived there from '95-'05. My last house was at 103rd and Indiana. I miss the small town feel that Lubbock had pretty often.

[Tomcat088]

Howdy LongtallTechsan , get your guns up buddy!! I had seen your name before and wondered if you went to Texas Tech, but then I discounted it and thought, naw, he just went to some other Tech school. It's awesome to see a fellow Red Raider around. That was a fun area that you lived in, all those houses out there. Lubbock is doing well, still great times and that small town feel. The traffic is getting worse it seems like each year, and the cops have cracked down lately after some drunk driving incidents, but overall, it's still the same. If you need any more help with those numbers or anything else, just let me know and I'll be happy to try to help you out. Take care.

[longtalltechsan]

Good to talk you Tomcat and find someone from my old stompin' grounds. Thanks for the help and I'll be sure to let you know if I need some help. Take care.