MOA clarification


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Franco2shoot
December 31, 2007, 05:18 PM
This is gonna be an easy one for the senior ones out there.

Over the weekend I was testing a 165 BTSP Hornaday versus a 168 BTHP Black hills in 308. One group (the Black hills ammo) is all within a circle with a radii of 1 inch(2 inch diameter). The Hornaday hits were in a circle with a 2 inch radii. So for me, bag the definitions, the Black Hills delivers better performance. However, when talking 1 inch Moa's how does one measure. For 1 inch MOA do I pick a center point and measure out 1 inch or is it 1 inch in diameter?

BTW there are a few "Flyers" for both, I'm not that hot of a shooter yet.....I've gotten fairly good at breath control(3 deep pausing on third letting cross hairs settle then squeeeeeeeze), now if I can just get over the "Trigger Jerk". Practice, Practice, Practice....
Thanks
KKKKFL

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dmftoy1
December 31, 2007, 05:39 PM
A minute of angle is slightly more than 1 inch at 100 yards but the generally accepted way of measuring it is to measure the diameter of the smallest circle that will completely encircle all your holes and then subtract the bullet diameter of what you're shooting. So if a 1 inch circle fits around your group and you're shooting a .308 then your group size is .692 and that's pretty good shooting in my book!

Have a good one,
Dave

taylorce1
December 31, 2007, 05:40 PM
The proper way to measure a shot group is to measure the outside edges of the two farthest points in the group and then subtract the diameter of the bullet. This will give you the shot group size center to center. If you have a set of dial calipers this will give you a more accurate shot group size, if not use a machinest rule which is graduated to 32nds. Hope this helps.

Oh yeah fliers count too unfortunatly.:(

Outlaws
December 31, 2007, 06:13 PM
You do not subtract the diameter of the bullet, you subtract the diameter of the bullet hole. The two do no equal the same thing.

deth502
December 31, 2007, 06:37 PM
moa is a measurement of angle.

a circle is divided into 360 degrees, each degree is div into 60 min, each min div into 60 seconds.

i "moa" is 1/60th of 1 degree of angle, so the actual distance between shots depends on the distance from the target.

immagine you took a shot at a target, then turned the muzzle of the rifle 1 degree. at 10', those 2 holes would be verry close. at 100yd, thay would be about 60" apart. at 200yd, they would be about 10' (120") apart. this would be 60 moa.

deth502
December 31, 2007, 06:42 PM
btw, in case i didnt make it clear, moa does NOT depend on distance.

when people say "it shoots .5 moa at 300 yds" the "300yds" is irrelevant. it shoots .5 moa at 5 ft and 500 yd too (as long as the shooter does their part)

moa is moa reguardless of distance.

the distance between the bullets will be greater at farther distances for the same moa.

Franco2shoot
December 31, 2007, 07:18 PM
Yikes!!!!!
OK for a simple "Close enough" kind of answer. The Black hills ammo put 8 bullet holes all within a circle that has a 1" radius. For folks from Rio Linda that is a Pie plate that is 2 inches across and the target was 100 yards down range. The Hornaday ammo produced a pattern a little bigger, say 3 inches across. Since I did not have the rifle bolted into a rock sled, some of this is due to operator error, but it became obvious to me that the Black hills ammo was producing better results.

With the Hornaday I hit the edge of the bulls eye once whereas with the Black hills, I shot the red dot out. Both are 1 deer MOA, but I would like to talk intelligently about MOA's hence the question.
KKKKFGL

Jenrick
December 31, 2007, 08:07 PM
In short 1 MOA is approximately 1" per 100 yds, so 1 at 100, 2 at 200, etc.

So at 100 yds if the rounds all fit in a box 1 inch square, you're shooting 1 MOA. From what you've described the Black Hills is shooting 2 MOA, and the Hornady is shooting 3 MOA.

The actual group size can be measured a whole lot ways. I just check to see if it's fit under a quarter, nickel, or dime. I really could care about the actual group measurement. Getting all rounds under a quarter is good enough for any purpose I will have. Getting them under a dime all the time is a personal goal that I strive for.

-Jenrick

JohnKSa
December 31, 2007, 09:44 PM
You do not subtract the diameter of the bullet, you subtract the diameter of the bullet hole. The two do not equal the same thing.Exactly correct. Sometimes the bullet holes will be of bullet diameter, but usually that is not the case. The Black hills ammo put 8 bullet holes all within a circle that has a 1" radius.Group size is the distance between the centerpoints of the two rounds that hit farthest apart on the target. Or, if you prefer, it is the DIAMETER of the circle that goes through the centerpoint of the two rounds that hit farthest apart on the target. It is a diameter measurement, not a radius measurement.

The group size in your case would be 2 inches, or about 2 MOA at 100 yards.

MOA stands for Minute Of Angle. Angles are measured in degrees, and there are 60 minutes in each degree. So there are 21,600 minutes in a full circle (360 degrees times 60).

If you picture yourself at the center of the circle then your target is on the circumference of the circle and the distance from you to your target is the radius of that circle. You can now measure distances on the target by using angles.

For a 100 yard circle, the circumference of the circle is about 22619.5 inches and if we divide that by the number of minutes in the circle (21600) you find out that there are about 1.047 minutes of angle per inch at that distance. Obviously if you increase the distance to your target the circle gets larger and there will be more minutes of angle per inch. Most of the time people just approximate one MOA as one inch at 100 yards, 2 inches at 200 yards, etc.

A simple formula that will get you very close to the actual number for MOA (in inches) at a given distance is as follows.

1 MOA = D / 95.5 where D is the distance to the target in yards.

Or, if you have a measurement of a group in inches, you can convert it to MOA with the following formula.

MOAGS = INCHGS * 95.5 / D where MOAGS is the Group Size in MOA, INCHGS is the Group Size in Inches and D is the distance to the target in yards.

MachIVshooter
January 1, 2008, 01:38 PM
when people say "it shoots .5 moa at 300 yds" the "300yds" is irrelevant. it shoots .5 moa at 5 ft and 500 yd too (as long as the shooter does their part)


Uh-uh. A rifle/ammo combo that shoots MOA at 100 yards will not necessarily maintain MOA at 500 yards.

deth502
January 1, 2008, 01:48 PM
Quote:
when people say "it shoots .5 moa at 300 yds" the "300yds" is irrelevant. it shoots .5 moa at 5 ft and 500 yd too (as long as the shooter does their part)

Uh-uh. A rifle/ammo combo that shoots MOA at 100 yards will not necessarily maintain MOA at 500 yards.

yes, moa is moa reguardless of distance. its geometry.

jmr40
January 1, 2008, 03:06 PM
I agree with MachIVshooter. In theory it should be simple geometry but it does not work that way in real life all the time. Have seen rifles that would do no better than 1 1/4" at 100 yards but shoot 1 3/4" at 200. At longer ranges there are a lot of other factors that come ointo play.

MachIVshooter
January 1, 2008, 03:32 PM
yes, moa is moa reguardless of distance. its geometry.

I'm not arguing that the measurement of MOA is constant. It the ability of a rifle/cartridge to maintain MOA at various distances that isn't.

No matter the quality of the bore and bullet and how well matched bullet weight and rifling rate are, all bullets oscillate around the trajectory axis. As distance increases and bullet speed drops, stability deteriorates and groups open up. This is why rounds with higher velocities coupled with bullets that have lower drag coefficients are capable of greater accuracy at increased ranges. A .22 target rifle that can put countless rounds into a single, tiny hole at 50 feet will not be sub-MOA at 200 yards, period.

And, of course, this does not even account for environmental factors like wind and humidity.

Franco2shoot
January 2, 2008, 11:54 AM
One final note on this topic... and correct me if I am wrong but it would seem to me that if one was talking the hard core capabilities of a specific rifle, that rifle should be locked down in some sort of vise system that removes the operator error.

Even if you gave me a super accurized rifle, I'ld prolly wobble and be unable to keep the holes within 1 MOA at 100 yards. Maybe some time in the future with lots more practice. Having said this, it was noticable that I could do better with Black Hills than I could with Hornaday.
KKKKFL

MGD 45
January 2, 2008, 12:10 PM
Well keep in mind that you could've had a better "lot" of bullets in the Black Hills than the Hornady box. If you shoot enough, you might discover the flip side one day where the Hornady shoots better than the Black Hills. I would probably shoot more than just 3 or 5 rounds to judge the ammo. More like several boxes....

Outlaws
January 2, 2008, 05:46 PM
One final note on this topic... and correct me if I am wrong but it would seem to me that if one was talking the hard core capabilities of a specific rifle, that rifle should be locked down in some sort of vise system that removes the operator error.

I just got the Caldwell Rock BR for Christmas. That with a Protektor bag for the rear is a nice combo and will be steady enough for most people to shoot bugeye groupings if their rifles/ammo are capable of it.

Tarvis
January 2, 2008, 11:31 PM
Minute of angle can roughly be described as 1 inch and 100 yards. Describe your groups in inches. Measure as described in post 3 and clarified in post 4.

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