- Feb 4, 2013
- 28,175
No, SI is not the metric system.
Metric degrees are degrees Centigrade. SI degrees are degrees Kelvin. The units are the same, but the base is not.
Unless you see temps described as 302 degrees today.
MOA vs MRAD
- Thread starter shocker998md
- Start date
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No, SI is not the metric system.
Metric degrees are degrees Centigrade. SI degrees are degrees Kelvin. The units are the same, but the base is not.
Unless you see temps described as 302 degrees today.
StickShaker
Active Member
I'm curious about which measurement myself and found this easy to read article. There is also a scope buyers guide link at the end of the article.
http://precisionrifleblog.com/2013/07/20/mil-vs-moa-an-objective-comparison/
http://precisionrifleblog.com/2013/07/20/mil-vs-moa-an-objective-comparison/
W2D
Ultimate Member
I was doing some quick calculations and wanted to share, so I dusted off this thread.
One of the advantages of MOA is at the range at 100 yds. The math is fairly elegant, such that 1 MOA projected on a target at 100 yards reduces down to pi/3 inches, or 1.05 inches, or about an inch at 100 yards. If your scope has 1/4 MOA clicks, 1 click moves the aim point 1/4". 1 click on a 1/2 MOA click scope moves the aim point 1/2". Double the yardage doubles the movement.
Math:
(I call "aimpoint" the measurement on the paper target.)
The sine of the angle in radians is very, very close to the angle in radians. For 1 MOA, the error is something like 0.00001%. That means instead of doing trig, just the ratio of the range and the aimpoint is all that is needed. The math using 1 MOA (1/60 of a degree is one Minute Of Angle), and using the conversion of pi/180, and finally 1 yard = 36 inches:
Sin (1/60 *pi/180) = pi/(60*180) = aimpoint/(100 yds *36 in/yd)
aimpoint = 100*36*pi/(60*180) = pi/3 inches = 1.05 inches
Using Mildot is the similar math actually, 1 mildot is 1/1000 of 100 yards, or 3.6 inches. A 1/10 mildot click moves the aimpoint .36 inches on the target.
One of the advantages of MOA is at the range at 100 yds. The math is fairly elegant, such that 1 MOA projected on a target at 100 yards reduces down to pi/3 inches, or 1.05 inches, or about an inch at 100 yards. If your scope has 1/4 MOA clicks, 1 click moves the aim point 1/4". 1 click on a 1/2 MOA click scope moves the aim point 1/2". Double the yardage doubles the movement.
Math:
(I call "aimpoint" the measurement on the paper target.)
The sine of the angle in radians is very, very close to the angle in radians. For 1 MOA, the error is something like 0.00001%. That means instead of doing trig, just the ratio of the range and the aimpoint is all that is needed. The math using 1 MOA (1/60 of a degree is one Minute Of Angle), and using the conversion of pi/180, and finally 1 yard = 36 inches:
Sin (1/60 *pi/180) = pi/(60*180) = aimpoint/(100 yds *36 in/yd)
aimpoint = 100*36*pi/(60*180) = pi/3 inches = 1.05 inches
Using Mildot is the similar math actually, 1 mildot is 1/1000 of 100 yards, or 3.6 inches. A 1/10 mildot click moves the aimpoint .36 inches on the target.
OrbitalEllipses
Ultimate Member
The issue with MOA is the leftover .05 which adds up to quite a bit of error at ELR distances. 1" per hundred yards is crude and not true MOA.
W2D
Ultimate Member
A whole 1/2" difference at 1000 yards? Like I said, at 100 yards, I find it easy to use. YMMV.
- Feb 4, 2013
- 28,175
If you have the appropriate reticle, there is no math.
Measure the offset between POA and POI, and adjust it.
Why convert at all?
Measure the offset between POA and POI, and adjust it.
Why convert at all?
W2D
Ultimate Member
The idea is to have a zeroed rifle, and hit a target at any range on the FIRST shot.
Really, I just like the beauty of how the 1 MOA works out to pi/3 at 100 yards. Nothing more.
OrbitalEllipses
Ultimate Member
When you dial your DOPE you are multiplying that 1/2" error.
TheBulge
Active Member
- Mar 7, 2011
- 344
W2D
Ultimate Member
I did a little more back of the envelope calculations using the path drop numbers for .223. You were right, that .05 MOA does add up over long distances, because a .223 bullet is dropping like a spitball at 600-1000 yards. The error from estimating 1.0" instead of 1.05" per MOA is about 22" at 1000 yards, but then again, the aimpoint is 36 feet above the target.
At a max useful range of 600 yards (ha!) the aimpoint is 7 feet above the target, and the 0.05 MOA causes about a 3.5" error, disregarding the resolution of the clicks.
I'm sure a flatter trajectory would be less error, but who knows how accurate a scope click really is. I read about adjusting windage and elevation a set number of clicks to shoot corners of a square box, but the author said that's almost always useless using medium cost scopes.
I'm back to agreeing with you about DOPE, but it was interesting to see for myself how the calculations worked out. Peace.
W2D
Ultimate Member
True beauty is 1/1000th for any unit of distance.
.
I agree. Isn't the metric system great?
j/k!
HawaiiMark
Member
Sort of, at 100 yards a MRAD is about 10 cm so 0.1 MRAD is about a cm. It's not metric but is sort of correlates to metric vs. MOA which sort of correlates to inches.
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