What does MOA means?

[Trickymissfit]

Fifty years ago I was working in a wood shop. The boss told me the chairlegs needed to be drilled for the stretcher at 5 degrees. I don't remember ever seeing a degree tool so I used minutes of angle and got so close no one noticed I didn't use some kind of tool. I guess I got lucky.

Honestly I had zero idea what a minute of angle meant forty years ago. Yet I'd had trig and calculus. Never totally understood it, and what it meant in the real world. Yes I heard the term arc seconds a few times here and there, but that was about it. In the mid 1980's I was introduced to the term again, but this time I learned to use it. I learned the black art of cutting surface plates to the Fed's lab grade spec. Being able to see a tenth of an arc second show up on an autocollimator made it easier to understand the concept. Otherwise I had no idea what or why. Suddenly one day while laying ontop a cold piece of granite I saw the triangle generated from the bench to the target 100 yards out. Then I started experimenting to see just what I could do with this new found concept in measurement.
gary

 

[Bart B]

One MOA of latitude is one nautical mile.

The rear sight windage knob on M1 and M14 service rifles has 32 threads per inch. Exactly, how many inches does 2 clicks on the knob move the line of sight at 100 yards on target for each rifle?

 

[Trickymissfit]

One MOA of latitude is one nautical mile.

The rear sight windage knob on M1 and M14 service rifles has 32 threads per inch. Exactly, how many inches does 2 clicks on the knob move the line of sight at 100 yards on target for each rifle?

would depend on how many clicks per turn of the thread or nut. My uneducated guess (been forty five + years since I shot an M14 with peep sights) would be a minute of angle or perhaps thirty seconds.

some time I'll tell you about a 20 year old kid with a N.M. M14 with peep sights shooting long range for keeps
gary

 

[Bart B]

From SAAMI:

MINUTE OF ANGLE (M.O.A.)
An angular measurement method used to describe accuracy capability. A minute of angle is one sixtieth of a degree, and subtends 1.047 inches at 100 yards, which for practical shooting purposes is considered to be one inch. A minute of angle group, therefore, equals one inch at 100 yards, two inches at 200 yards, etc.

 

[Trickymissfit]

From SAAMI:

MINUTE OF ANGLE (M.O.A.)
An angular measurement method used to describe accuracy capability. A minute of angle is one sixtieth of a degree, and subtends 1.047 inches at 100 yards, which for practical shooting purposes is considered to be one inch. A minute of angle group, therefore, equals one inch at 100 yards, two inches at 200 yards, etc.

yes but now we see SAAMI's errors start to stack up. You use 1.047", and I round up to 1.048" . Not much difference of course. Now we take the next .048" and trig it out to 1,000 yards. Close to a half inch! Means little shooting an elk, but shooting 1,000 yards targets it does mean everything.

Just another error from SAAMI
gary

 

[FEENIX]

I am knew to guns and hunting. Recently I came across an article referring to MOA. No description of the term was given. I supposed its assumed that readers know what it means. I have Google it and have searched in many places but can't find an answer.

Thank you for your help.

Keep it simple, he's got you squared away from the get go ...

Minute of Angle (MOA) | National Shooting Sports Foundation

 

[Bart B]

yes but now we see SAAMI's errors start to stack up. You use 1.047", and I round up to 1.048" . Not much difference of course. Now we take the next .048" and trig it out to 1,000 yards. Close to a half inch! Means little shooting an elk, but shooting 1,000 yards targets it does mean everything.

It's has never meant everything in bullseye long range matches. Never ever heard anyone talk, worry or mandate any such thing. Traditionally, it means nothing.

Nor do I comprehend how it would matter in group shooting at long range. Especially when the groups are measured in inches and the stat office doesn't know exactly how much each competitor's scope adjustments are to the nth degree of adjustment per click. Ahd the best of them cannot read wind condition changes accurately to less than 1/3 MOA. The backlash error for most scopes with a +/- 1 click change is a lot more than the ~1/20th MOA difference between simplified MOA vs exact MOA.

Consider long range matches shooting M1 or M14 service rifles. Garands with their Nat'l Match rear sight up 10 clicks from the bottom move bullet impact for 2 clicks about 10.24" at 1000 yards per click zeroed at that range. Who really does care that it's not exactly 10.47197536428328546947470696664 inches for 2 clicks of windage?

Nobody can read condition changes precisely enough for 1000-yard stuff to warrant any adjustment causing any less than 3 to 4 inches. The US Palma Team rifles have sights with about 1/2 MOA clicks.

So, Gary, maybe you could explain the details of how one would manage exact numbers "meaning everything" in a long range match and consistently get better results than using approximations that have worked very well for decades. Then, maybe, I'll understand.

 

[Mikecr]

This is a LR HUNTING site and not a LR MATCH site.
That seems a difference you don't understand Bart.

 

[CEIBA]

Thank you to all.

 

[Waynard]

Ceiba, do you think you understand all that was posted here?

 

[KYpatriot]

Ceiba,

LR hunting vs LR match, makes no difference. A moa is a moa. A mil is a mil. Both are angular measurements that have an exact mathematical meaning, which was explained (1 moa = approx 1.047 in at 100 yards).

Do a precise tall target track test on your scope first of all, as many scopes even high end ones, will not always track to within difference we are talking about at 1000 yards. always track test to save yourself aggravation later. Use true moa for this if thst is how your scope is labeled.

There is no reason not to use moa correctly, if that is what your scope is labeled, but test it to be sure. Let me know if you dont know what I mean by a tall target track test.

Lets go over a shot example to illustrate the difference.

For example for my 7 mag using 180 hybrids my ballistic app for a shot calls for a dial up of 22.25 moa to get to 1000 yards. If my scope tracks true (again not something to take for granted regardless of what you paid for it) then I would dial up 22.25 moa. The drop in inches for that shot is 232.7 inches. It would take 89 of the 1/4 moa clicks to dial 22.25 moa, or 232.7 inches at 1000 yards.

For scopes calibrated in inches per hundred yards (iphy), it takes 93 1/4 inch clicks to come up 232.7 inches at 1000 yards

If I used the iphy solution (93 clicks) on a true moa scope, I would in fact be dialing 23.25 moa instead of the required 22.25 moa, and thus would be a little over ten inches high. Conversely, if I used the moa solution on an iphy scope, Id be ten inches low at 1000.

So it matters. Make sure your units in the ballistic app match your scope, and that you have verified your scope indeed travks in acvordance with how it is labeled.

For Bart,

You likely have more experience than I at 1000 yard shooting, but in this case you are forgetting that hunters typically zero at 100 yards, and certainly not 1000 yards like a target competitor. Hunters never know what range they will shoot in advance, so they are dialing up from a short range zero for each shot. That changes everything.

When you are zeroed at 1000, and you adjust a click or two, then the difference in a 1/4 iphy click and a 1/4moa click is tiny and could safely be ignored. If you are dialing up from a short range zero for a long range shot, we are adjusting, 80, 90, 100, or more clicks. That tiny difference times 90 is not so tiny anymore. In my real world example above it was ten inches, in a lessor performing round like a 308 it would be over 15 inches.