OK Sniper guys - why are these reticles marked oddly?
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Thread: OK Sniper guys - why are these reticles marked oddly?

  1. #1
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    Default OK Sniper guys - why are these reticles marked oddly?

    Here is a little brain teaser. A collector in France, who has much better eyes than I have, picked up on the fact that Japanese sniper rifle scope reticles and MG scope reticles, have vertical line graduations that tilt to the right as the ranges increase. This is true of Type 97 sniper rifle scopes and Type 96 MG scopes. These weapons are chambered for the Japanese 6.5x50SR cartridge. I checked my Type 97 scope and he is correct. I also checked several photos of other T97 scopes and again I can see the tilt.

    Oddly, to me at least, this is not true of the later Type 99 sniper rifle scopes, nor the Type 99 LMG scopes. These weapons are chambered for the 7.7x58 Japanese cartridge.

    What were the Japanese trying to adjust for? Perhaps the effect of the twist of the projectile in the rifling? Some kind of windage compensation? I do not have a clue.

    The attached photos are of the T96 and T97 reticles, then close ups of the images with a perfectly straight red line added for clarity. I have not attached Type 99 sniper rifle, nor Type 99 LMG scope reticle photos as they are simply "normal."

    Does anyone have the answer? Any help would be appreciated.

    Frank
    Attached Thumbnails Attached Thumbnails LV T96 lmg picture.jpg  

    LV T96 lmg zoom.JPG  

    LV T97 ret 2.JPG  

    LV T97 zoom ret.JPG  

    Francis C. Allan
    20 Courtney Place
    Palm Coast, FL 32137-8126
    (386) 445-4225

  2. #2

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    That's really interesting! Is it possible the 6.5mm scopes are more offset than the 7.7mm ones and these odd stadia lines compensate for that? I've never compared them side by side. Perhaps they realized that an angled reticle wasn't actually necessary to compensate for the scope offset and so did away with it on the later manufactured scopes? Just wild and uninformed guesses on my part.

  3. #3
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    Dear WolfmanReid:

    Your thoughts make some sense. I guess no one here has seen this on scopes from other countries?????

    Frank
    Francis C. Allan
    20 Courtney Place
    Palm Coast, FL 32137-8126
    (386) 445-4225

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  5. #4
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    My guess is they are compensating for the drift that a bullet from a right-hand twist barrel will have.

    As the bullet flies downrange, aerodynamic forces will cause it to continue to travel nose-on as the trajectory continues to turn downward. This tilting of the bullet creates gyroscopic forces on the bullet (like what happens when you try to tilt a gyroscope) that will cause the bullet to yaw and drift off to the right.

    If the bullet were fired from a left hand twist barrel, it would drift to the left.

    Snipers are trained about this long range drift, and learn to adjust for it.

    I haven't seen this on other scopes, but you also see this same sort of long range drift compensation built into the 1907 rear sight on the 1903 Springfield.

    EDIT: You will also notice that the 6.5 mm reticle is set up for significantly less drift than the 7.7mm. The presumed explanation for this is that the smaller diameter bullet will have a lower moment of inertia, and thus less rotational inertia, and will yaw a smaller amount as it continues point-first along its trajectory.
    Last edited by Ronbo6; 03-07-2017 at 04:01 PM. Reason: More Info

  6. #5
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    Yes, it reminds me of the drift built into the 1903 Springfield rear sight.
    Looking for PU scope # Б05115

  7. #6
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    I have noticed this in my 97 scopes,but do not have a 96 scope to compare. My 99 lmg scopes look to be straight up and down.
    I would say it would be for drift?

  8. #7
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    Thanks guys. I sort of guessed that, but I was not sure and I have seen nothing in the Japanese archives to corroborate my assumption.

    Frank
    Francis C. Allan
    20 Courtney Place
    Palm Coast, FL 32137-8126
    (386) 445-4225

  9. #8
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    Francis, the Japanese knew that they would be fighting in the hot, damp climates of the south pacific. Their approach to sealing the scope was to eliminate as many paths for moisture penetration as possible and simply to train their snipers to "hold off" target.

    By the same token the US approach was to buy whatever scope was available from the local sporting goods or hardware store. WW2 ordnance personnel accounts are full of tales of moisture infiltrating to Weavers and Unertls and putting them put of action.

    That is the real reason for the "tricky reticles".

  10. #9
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    Coriolis effect.
    "Enjoy every Sandwich" Warren Zevon

  11. #10
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    Quote Originally Posted by Hal O'Peridol View Post
    Coriolis effect.
    Not really. If it WERE Coriolis, the 'drift' would be opposite depending upon whether you were firing North or South.

  12. #11
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    Thanks guys.

    Frank
    Francis C. Allan
    20 Courtney Place
    Palm Coast, FL 32137-8126
    (386) 445-4225

  13. #12
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    Ronbo6 is right it was for rotational drift.

  14. #13
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    If the angle of deflection in the reticle is known then the drift theory should be provable for either cartridges ballistics. I would think?

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    I am impressed that they would build in spin drift. Must have been designed by a really picky, detail-oriented gent.

  16. #15
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    Quote Originally Posted by Graz View Post
    I am impressed that they would build in spin drift. Must have been designed by a really picky, detail-oriented gent.

    The designer was Japanese. Look at their cars. That is what they seem to do best.

    It beats the heck out of building a non-adjustable scope which would cause you to consistently miss at longer ranges.

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