Minutes of Angle Explained

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About Robert Farago

Robert Farago is the Publisher of The Truth About Guns (TTAG). He started the site to explore the ethics, morality, business, politics, culture, technology, practice, strategy, dangers and fun of guns.

11 Responses to Minutes of Angle Explained

  1. avatarRabbi says:

    Decent explanation.

    MOA is a very simple concept, however, it is not a simple task to explain it to a new shooter!

    The speaker should have started off by explaining that scope adjustments are done in MOA (most;some are milrad) so the shooter just needs to figure our the point of impact change measured in MOA so it can be translated to the scope.

    If anyone has any questions, I will be glad to assist.

  2. avatarRalph says:

    NSSF should rename this video “Hours of Angle.” I’ll watch it later tonight, ’cause I’m all out of Lunesta.

  3. Best explanation of MOA that I’ve ever seen!

    I spent 30 minutes at the range last weekend watching a father try to explain MOA and zeroing a scope to his son. Two other shooters came over to correct the father and then three more guys came over to correct the first two. Not once did anyone say “minute of angle” (LOL).

  4. avatarMagoo says:

    This is a good practical explanation of minute of angle, but the description of gravity is problematical. (That is, it could make your HS physics teacher’s head explode.) At about 5:00 the instructor says, “A bullet that is traveling slower is exposed to gravity longer and therefore it falls faster.” More accurately, a bullet’s vertical motion is entirely independent from its horizontal motion. A bullet will accelerate toward the earth at a uniform rate (9.8 m/s^2) regardless of its forward velocity, and will fall at that rate from the instant it leaves the barrel.

    Fired from a horizontal line of departure, i.e., with the barrel parallel to the earth, and regardless of its forward velocity, a bullet will strike the ground at exactly the same instant as a bullet dropped from one’s hand at the same height. From a height of 60 inches (and in a null fluid medium, etc) approximately .55 seconds. The bullet’s forward velocity determines the horizontal distance traveled downrange in that time.

    So we might start here: The line of sight (LOS) is a straight line, while the bullet’s trajectory is a parabola intersecting the LOS at two points. The sight’s minute of angle (with the barrel) is adjusted to make the shooter’s line of sight and the bullet’s trajectory meet at the same point on the target.

    • avatarTTACer says:

      “A bullet that is traveling slower is exposed to gravity longer and therefore it falls faster.”

      This is not, strictly speaking, untrue. He said it “falls faster”, not that the rate at which it accelerates towards the earth increases.

      If the bullet is accelerating towards the earth at a constant 9.81 m/s2, then after 3 seconds it would be falling at 28.43 m/s. At least that’s how I read it.

      • avatarMagoo says:

        Sure, and in three seconds a bullet will fall over 44 meters — regardless of its forward velocity. The confusion arises not in suggesting that a bullet falls faster as it slows down but that its horizontal velocity has any influence on its rate of drop. The bullet will drop at the same uniform rate as any falling body subject to gravity. You can roll it off the table or fire it from a rifle and it will still fall ~44 meters in 3 seconds unless something stops it. The horizontal velocity doesn’t matter.

        Whether the bullet slows from 4,000 fps to 2,000 fps or 900 to 100 fps as it travels downrange from zero departure angle, it will still drop at the same rate vs. time and hit the ground at the same instant. The slower bullet just won’t travel as far downrange before it hits the ground. This is why the slower bullet exhibits a deeper parabola. The vertical rate of drop remains identical because gravity is constant.

        Except with the Lippard A2, apparently.

    • avatarCleckner says:

      Great catch Magoo!

      As the instructor in the video, I had to go back to check what I said since I completely understand and agree that horizontal motion will not effect vertical motion and often use the very example you did to explain this theory to students.

      As I went back to see what I said, I realize that I did say that part incorrectly. I was trying to explain the idea that for each 100 yards the bullet travels, it drops further and further – from 100-200 yards, it drops a lot less then it drops between 800-900 yards. “Faster” was the wrong term – I should have said “further.” If you watch the part just after, I do a bit better job explaining what I mean when I reference the time it takes to travel each 100 yard gap.

      When the bullet is traveling faster, it is exposed to gravity (during that 100 yard gap) for a shorter period of time than it is when it is travelling slower. So, a bullet obviously falls a shorter distance in a fraction of a second than it does in a full second. And of course since its rate of fall is an acceleration, the longer it falls, the faster velocity it has as it falls (up to terminal velocity, of course).

      In some of the future videos I am going to explain wind in a similar fashion. The forward speed of the bullet has no effect on the side to side drift due to wind directly. However, the reason wind will affect the bullet more at longer distances has to do with the amount of time the bullet is exposed to that wind. 10mph side to side wind for a 100 yds target gets a chance to blow on the bullet for a shorter period of time and will therefore move the bullet less than a 10mph side to side wind for a 800 yd target with a longer exposure. It is not the slowing of the bullet that allows it to be affected more by the wind alone, but rather the slowing of the bullet exposes it to wind longer and longer each 100 yards.

      You guys have a very good grasp on the topic and I appreciate you keeping me accurate! Had this been a classroom and you called me on this, I would have welcomed the opportunity to say it correctly or clarify what I meant.

      As far as the content or the length of the video goes, we are trying to make VERY basic videos covering these topics in very SIMPLIFIED terms to help beginners. If you guys think of an idea for some more basic topics to cover, or would like to have input on future videos, I welcome your comments and suggestions! You can email them to me at rcleckner@nssf.org. The better the videos are, the more educated shooters we have and the more we support the shooting community.

      • avatarMagoo says:

        Thanks for the kind words. I found the video excellent; the depiction of gravity was only a quibble and more to do with a point of physics than with firearms specifically. Please keep up the great work.

  5. avatarRabbi says:

    What the presenter is trying to say (or, should have said) is that the slower the bullet travels the more effect gravity has on it over a given distance.

    I know that this is not exact or even possible, I am just throwing out numbers for a better understanding: Let’s say that the bullet is traveling through the first 50 yards of it’s path at 2,000 fps and 1,000 fps for its last 50yards, the drop due to gravity would be twice a large on it’s last leg than the first because it is taking twice as long to transverse the same 50 yards.

  6. avatarhomobangbangamus says:

    I can’t stop laughing!

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