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View Full Version : MOA is MOA, regardless of range right?


Donut
07-14-2008, 9:13 PM
I went to Iron Sights yesterday (25 yard indoor) and tried out my new cheap BSA scope on a cheap "Famous Maker" carry handle mount, with cheap rings ($5 @ Wal-Mart). I put it all on my 16-inch CMMG Mid-Length MedCon upper.

http://i4.photobucket.com/albums/y131/guttedhatch/scopetarget.jpg

0.55 - 0.224 = 0.326 inch center-to-center group @ 25 yards.

By my math, that's 1.3 MOA... Not bad for basic gear and my first time shooting through a scope (and only the second time out with my AR), if I do say so myself.

I'm pretty damn impressed with the out of the box CMMG upper.

Corbin Dallas
07-14-2008, 9:19 PM
The quick answer - at 25 yards, no. At 100 yards, yes.

Edit: Found it...

Minute-Of-Angle
The term "minute-of-angle" (MOA) is used regularly by target shooters at the range, but is probably understood, thoroughly, by few (the same goes for mil-dots). Defined loosely, one MOA = 1" @ 100 yards; so, if you shot your rifle 5 times into a 100-yard target and every shot went into a one-inch circle you had drawn on the paper, then your rifle could be said to shoot 1 MOA. Likewise, if every shot goes into a two-inch circle at 200 yards, then you're shooting 1 MOA. A 10-inch group at 500 yards would be 2 MOA.

Now for the fun part. There are 360 degrees in a circle. Each degree can be broken down further into minutes. There are 60 minutes in a degree. Likewise, there are 60 seconds in a minute. Now, to figure out the distance subtended by 1 minute at any particular distance, we need merely to plug those two values into a simple trigonometric equation. The tangent function fits the bill nicely. Here's the equation:
tan(angle) = distance subtended/distance to the target (units must be consistent--e.g., 1/36 of a yard [1"] divided by 100 yards)

Now, we know the angle (1 minute or 1/60 of a degree) and we know the distance to the target (100 yards), but we need to figure out the actual distance subtended at the target (i.e., is 1 MOA actually 1" @ 100 yards?). What we need to do is solve for "distance subtended." Here's our final equation:
tan(angle)*distance to the target = distance subtended

Make sure your calculator is in "degree" mode (as opposed to "radian" or "gradian") and type in 1/60 (for degrees) and hit the "tangent" button. Then multiply that by 100 yards. This should give you the distance (in yards) subtended at 100 yards. Multiply this by 36 to get inches. The answer should be:
1.047197580733"

This is just a hair over the commonly quoted "one inch." At 1000 yards, this would be almost 10 1/2 inches. Apparently, it is just a coincidence that 1 MOA happens to be REALLY close to 1" @ 100 yards. It is, however, quite convenient.

Timberwolf
07-14-2008, 9:22 PM
Your math is right - that would be approx 1.3 MOA using shooters MOA

Donut
07-14-2008, 9:25 PM
The quick answer - at 25 yards, no. At 100 yards, yes.

Edit: Found it...

Ok, so 1.352 MOA, to be precise.

J_Rock
07-14-2008, 9:28 PM
Why are you excluding the other 2 rounds?

One Shot, One Dropped
07-14-2008, 9:32 PM
Velocity differences could affect the final outcome (in MOA) due to different rates of drop, and variations in bullet properties could yield different twist rates. Both yield different trajectories which could affect spread. PPU isn't that bad, though.

CSACANNONEER
07-14-2008, 9:33 PM
Yep, your right. The only possible "problem" that I see is if you believe that you can easily do the same in outdoor conditions while shooting at farther distances. I've found that, although I can routinely shoot <moa at 100 yards, by the time I stretch it out to 1000 I'm averaging a little over 1.5 moa. I'm not knocking your impressive achievement. I'm just letting you know that when you get outside and shoot at longer distances, you may not be able to consistantly shoot like that.

sloguy
07-14-2008, 9:38 PM
Why are you excluding the other 2 rounds?

good question.

Donut
07-14-2008, 9:45 PM
Why are you excluding the other 2 rounds?

That's another 3 round group, but it measures 0.376" center-to-center. :p


Yep, your right. The only possible "problem" that I see is if you believe that you can easily do the same in outdoor conditions while shooting at farther distances. I've found that, although I can routinely shoot <moa at 100 yards, by the time I stretch it out to 1000 I'm averaging a little over 1.5 moa. I'm not knocking your impressive achievement. I'm just letting you know that when you get outside and shoot at longer distances, you may not be able to consistantly shoot like that.

Believe me, I have no delusions about my shooting ability. Like I said, it's only the second time I've shot my AR. The main bug that got me to buy the scope in the first place was to make sure the rifle was capable of decent mechanical accuracy so that I know that all the poor groups I'm bound to put together with iron sights are me. I've probably got less that 700 rounds through both my rifles, and 400 of those are through my Saiga. So to say i am an inexperienced rifle shooter would be an understatement.

jacques
07-14-2008, 9:51 PM
There was a thread around here, or maybe a link to ARF. 3-round groups are not an accurate assesment. Have to do 5-round groups.

paul0660
07-14-2008, 10:28 PM
5 rounds, 100 yards. Or 50 yards, 5 rounds, and admit you don't know snot.

workinwifdakids
07-14-2008, 10:37 PM
That's another 3 round group, but it measures 0.376" center-to-center.

:rofl2:

You have to start with a 5-shot group at 100 yards. The reason is this: if the beginning distance were arbitrary, I could say that my gun shoots into the same exact hole from 6 inches away, and therefore is a 0.0MOA rifle.

By way of analogy, my car scooted forward a milimeter in 0.0002 seconds, and therefore goes 800 miles an hour. Sometimes things don't work to well like that.

So, run a 5-shot group at 100 yards. You can wait about a minute between shoots to cool the barrel. Hell, you could wait an hour, but it probably won't make too much difference. Remember, though: accuracy is affected greatly by loads, so don't get disgusted if your groups suck. Just find a different load.

sloguy
07-14-2008, 11:04 PM
before everyone continues mocking the guy, remember that they were new at this at one point as well. also keep in mind that we dont know what position he shot this in and what, if any rest he used. indoor ranges arent known for their comforts for shooting rifles.

id like to see what donut can do with a decent bench and some sandbags.

Donut
07-14-2008, 11:08 PM
5 rounds, 100 yards. Or 50 yards, 5 rounds, and admit you don't know snot.

You mean this wasn't enough of an admission? :p

Believe me, I have no delusions about my shooting ability... <snip> So to say i am an inexperienced rifle shooter would be an understatement.

:rofl2:

You have to start with a 5-shot group at 100 yards. The reason is this: if the beginning distance were arbitrary, I could say that my gun shoots into the same exact hole from 6 inches away, and therefore is a 0.0MOA rifle.

By way of analogy, my car scooted forward a milimeter in 0.0002 seconds, and therefore goes 800 miles an hour. Sometimes things don't work to well like that.

So, run a 5-shot group at 100 yards. You can wait about a minute between shoots to cool the barrel. Hell, you could wait an hour, but it probably won't make too much difference. Remember, though: accuracy is affected greatly by loads, so don't get disgusted if your groups suck. Just find a different load.
I would be happy to suck at 100 yards, because that would mean I was shooting at something further than 25 yards, which is all Iron Sights goes out to.

J_Rock
07-14-2008, 11:09 PM
Include the other 2 shots. Measure again and subtract the caliber. Then post back the results. Thats your real group size right there.I'm guessing which would put your group to about 1"

Donut
07-14-2008, 11:11 PM
before everyone continues mocking the guy, remember that they were new at this at one point as well. also keep in mind that we dont know what position he shot this in and what, if any rest he used. indoor ranges arent known for their comforts for shooting rifles.

id like to see what donut can do with a decent bench and some sandbags.

Sitting on a short barstool thing, resting the bottom of the grip on the booth shelf thing, and my left hand on the handguard.

Donut
07-14-2008, 11:15 PM
Include the other 2 shots. Measure again and subtract the caliber. Then post back the results. Thats your real group size right there.I'm guessing which would put your group to about 1"


I adjusted the scope's elevation between the two three-shot groups. :(

jacques
07-14-2008, 11:29 PM
I adjusted the scope's elevation between the two three-shot groups. :(

Lots O time to shoot and practice. Nothing wrong with your group.

I looked for the thread that had a link to the 3-shot vs. 5-shot group and can not find it. I believe AR15barrels pointed it out at one time.

I was just thinking and an excellent place to learn to shoot is the Project Appleseed events they have. It IS 25yd AQT targets. You will need about 400rds of Ammo and the price is ~75 for two days of training. I went to the first one in Cali. There were 70 people there. 3-walked away with a rifleman patch. It is not easy, I plan on going again.

CRTguns
07-14-2008, 11:31 PM
Why are you excluding the other 2 rounds?

Cause they're less desireable...:D

Donut
07-14-2008, 11:51 PM
Lots O time to shoot and practice. Nothing wrong with your group.

I looked for the thread that had a link to the 3-shot vs. 5-shot group and can not find it. I believe AR15barrels pointed it out at one time.

I was just thinking and an excellent place to learn to shoot is the Project Appleseed events they have. It IS 25yd AQT targets. You will need about 400rds of Ammo and the price is ~75 for two days of training. I went to the first one in Cali. There were 70 people there. 3-walked away with a rifleman patch. It is not easy, I plan on going again.

I have read a little about those. They look like fun, and I'll probably try and make one in August, if my work schedule permits, but definitely before the end of the year.

acheron800
07-14-2008, 11:57 PM
10 rd group by my girlfriend @ Iron Sights... Id say you did good since thats what I told her!...Hell Im a noob as well. Dont let these pro gnar boots war gunners get you down! :D

If you are ever down to go to iron sights shoot me a pm, maybe we could meet up!

http://a368.ac-images.myspacecdn.com/images01/47/l_b6cbab30c1569011c87467723e5218f7.jpg

jacques
07-14-2008, 11:59 PM
I have read a little about those. They look like fun, and I'll probably try and make one in August, if my work schedule permits, but definitely before the end of the year.

Definitely in August I am going again. I have put off my second one for too long. Work always gets in the way. Matter of fact, work tried to pull me out during the first one to send me to the Bahamas. They wanted me to leave on Sunday Morning and I had to tell them I couldn't leave until Monday. So I left on Monday.