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cheap red dot scopes

joshmb1982joshmb1982 Member Posts: 8,929
edited October 2009 in Ask the Experts
I bought a chepo red dot scope for my ak from CTD. i also put a cheap green lazer on it. noticed something odd about it though. i put the red dot on first and sighted it in at 50yds. then i put the lazer on it put the lazer so it met the red dot at 50yds. this is when i noticed somthing funny.

at 50yds the red dot and green lazer met. now if i aim at the ground and bring the lazer twords me or away it moves away from the red dot. now i know the lazer only goes in a straight line so that cant change. does this mean that the red dot is off at anything other then 50yds?

i know you get what you pay for but this just just make sense to me.

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    armilitearmilite Member Posts: 35,483 ✭✭✭
    edited November -1
    NO it just means you bought some cheap junk and you get what you pay for.
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    BeeramidBeeramid Member, Moderator Posts: 7,264 ******
    edited November -1
    The laser doesn't move(assuming the mount in tight), but it may appear to while looking through the red dot in motion.
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    beantownshootahbeantownshootah Member Posts: 12,776 ✭✭✭
    edited November -1
    quote:Originally posted by joshmb1982
    I bought a chepo red dot scope for my ak from CTD. i also put a cheap green lazer on it. noticed something odd about it though. i put the red dot on first and sighted it in at 50yds. then i put the lazer on it put the lazer so it met the red dot at 50yds. this is when i noticed somthing funny.

    at 50yds the red dot and green lazer met. now if i aim at the ground and bring the lazer twords me or away it moves away from the red dot. now i know the lazer only goes in a straight line so that cant change. does this mean that the red dot is off at anything other then 50yds?

    i know you get what you pay for but this just just make sense to me.

    This has nothing to do with the quality of the sights or laser, but simple physics.

    Imagine (just for ease of understanding here) that the red dot is a red laser and it projects a straight line.

    I don't know exactly how you mounted the green laser, but it can't be in the exact same axis as the red dot (otherwise you couldn't look through the red dot).

    In other words there has to be some space in between the red dot and the green laser. One has to be higher (probably the red dot), and one lower (probably the laser).

    So if each of the two is projecting its own absolutely straight beam, and the beams intersect at exactly 50 yards, then they *CAN NOT* intersect at any other point.

    More simply, two different straight lines can only intersect at one point.

    If you've made them intersect at 50 yards (by having them both hit the gun zero point at that distance), then they CANNOT match/intersect at any other point.

    The further away you get, the more the two beams will diverge. Also, the CLOSER you get, the more the two beams will diverge.

    Now, to answer the question **OF COURSE* the red dot is off at any distance other than where you zero it. That is true of *ANY* optical sight, whether its a red-dot, laser, or even an conventional optical rifle scope.

    Again, since an optical sight sights by light, which travels in a perfectly straight line, but the path of a bullet describes an arc (or parabola), the bullet path and red dot can only intersect at at MOST two points. . .one when the bullet is going UP and one when it is going DOWN.

    At any OTHER points in space, the sight line and the bullet flight path MUST diverge. So at any point other than where the gun is zeroed (and possibly one more point where the flight of the bullet intersects the sight line), the bullet will NOT strike exactly where the red dot is pointing.

    BUT. . .at relatively close distances (usually about 200 yards for most ordinary centerfire rifle bullets) the bullet path will be "close enough", that it won't make much of a difference, being off by only maybe 2-3 inches if the gun is sighted correctly.
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