 |  | | | |  | |  |  | Scope Knob Calibration Marks |  | |  |  | |
 Posted: Wed Mar 10, 2010 9:43 am |
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| Slavia |
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How do you use those calibration marks on scope adjustment screws/knobs?
Here is a BSA:
A Tasco:
And a cheap 15mm Crosman, that doesn't even have "clicks":
M.O.A. per click I understand. Counting clicks I understand. Up and down I understand. But those calibration marks - there is no reference mark like you would find on a micrometer, dial caliper, or vernier scale. They're too close together to gauge position by some sort of "landmark" point on the scope.
Is there a gap in my education, or are they only to give the appearance of a precisely calibrated instrument? |
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| Posted: Wed Mar 10, 2010 9:59 am |
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| oddtodd |
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| Now that you mention it, I've never seen any type of reference point either. Must be a case of make your own mark or leave it pretty. |
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| Posted: Wed Mar 10, 2010 11:59 am |
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| donec |
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| Look for a tiny small little white dot. My center point has one and I use it to see which mark I am at. My center point 6-16x40 has a hex screw on the top so that when I get it set to zero at say 35 yards then I can turn the hex screw and disconnect the marks allowing me to turn the marks back to zero then tighten the hex screw thus resiting the calibration. After doing that I can change the elevation or windage for a specific target and just go back to zero when I want it back to my 35 yard zero. I don't see how that would work without the mark. I guess you could add your own mark. |
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| Posted: Wed Mar 10, 2010 1:29 pm |
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| Slavia |
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| Quote: |
| My center point 6-16x40 has a hex screw on the top so that when I get it set to zero at say 35 yards then I can turn the hex screw and disconnect the marks allowing me to turn the marks back to zero |
That makes sense. Most measuring instruments will have some means of fixing the "zero" mark. I looked a little closer, and my BSA does have a reference mark and setscrew:
That's great, but even when my eyes were young I would have needed to use a magnifying glass to see the marks. That's true for all the scales I looked at. Some are ridiculously small, like this BSA red dot:
I looked at a couple more scopes, and none of the "coin-adjustable" turrets have reference marks. They all have the numeral "0" printed on them (see photos above), so I suppose they do intend for the user to scribe their own mark. That's also fine, but what happens if you remove the scope and later re-mount it? It's unlikely the zero will be exactly the same - do you then put up with multiple (and confusing) reference marks?
I guess I'm looking for a scale that can actually be read and used, like my micrometer:
I suppose you get what you pay for, and there are scopes with usable calibrations. The calibration marks on the ones I can afford are probably just to mimic the good ones:
So I'll continue to count clicks, and maybe inlet an abacus in the butt of my next project gun. |
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| Posted: Tue Mar 30, 2010 8:40 pm |
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| Quack |
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Here is a good download that explains 'zeroing' in for air rifles as well as trajectory, parallax, and some ballistics. Well it give a great explanation, whether I took it all in is another story.
www.viriato.net/airgunning/bfta_setup_manual.pdf |
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| Posted: Wed Mar 31, 2010 8:09 am |
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| Slavia |
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| That's an excellent piece. Thanks for posting it! |
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