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  #1  
Old 04-01-2009, 04:06 AM
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Lyman all american 4x scope


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I am trying to find the moa for this scope. I was told it is 1/2 but at what yardage? 100 or 50. (this is not the perma center model.) It was made mid 1960's. Hope someone can help.
Thanks LS
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Old 04-01-2009, 05:35 AM
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My recommendation is to test it yourself and see what the change in point of impact vs point of aim is. The elevation and windage may be different values. I'd recommend doing the box test (all at the same point of aim), where you fire 3 rounds at a target at 100yds, move the elevation up 10 clicks, 3 shots, right 10 clicks, 3 shots, down 10 clicks, 3 shots, left 10 clicks, and 3 more shots, which should be on top of the first 3, if the adjustments are sound. As with most of these older scopes, a couple taps on the adjustment housing after each adjustment should help to ensure reliability of tracking.

If you end up with a square, you know that elevation and windage adjustments are the same. If you end up with a rectangle, likely oriented horizontally, then the windage is probably twice the value of the elevation.

Good luck.
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Old 04-01-2009, 06:04 AM
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A Minute Of Angle is 1” at 100 yards, 2” at 200 yards ½” at 50 yards and so forth.
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Old 04-01-2009, 07:07 AM
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Argo is correct. The adjustments on the scope change the sight setting by half a minute of angle, or 0.008333... degrees. Dividing a degree into sixty minutes of angle and a minute into sixty seconds of a degree is an old practice rooted in using 360 as base number for determining angles and time and calendar days, form back when they were unable to clearly see that a year was not exactly 360 days. With your scope at the apex of the angle, the distance subtended by the sides of the angle (the distance your bullet will shift on the target when you adjust your sight one click) grows as you move further from the apex. Thus you have to know how far you are from the target to know how many inches one click on the setting knob or screw will move the bullet's point of impact?

A little more exact conversion is 1.05", or 1 and 1/20 inches per minute of angle sight adjustment (2 click on your sight) per hundred yards of distance. Most people can't shoot with the precision of 1/20 of an inch at 100 yards, so we normally just round it to 1 inch, as Argo did. So, at 100 yards each click of your sight will move the bullet about half an inch. Twice that much at 200 yards, three times that much at 300 yards, and so on. If you have a range finder and and a calculator and want a formula for the amount each click of adjustment on your sight should move the bullet:

multiply the number of yards distance to the target by 0.005 inches

and that will be more than close enough for practical work. You have to keep in mind that most real sight adjustments have some backlash and some mechanisms don't have the exact same amount of adjustment per click either side of zero, so any calculation could be off by a quarter of an inch per hundred yards, but overall the formula will be about right. Certainly it is all more precise than minute of whitetail until you get out beyond 400 yards, where doping the wind starts to become as important as knowing your elevation sight settings.
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Last edited by unclenick; 04-01-2009 at 07:15 AM. Reason: typo fix
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Old 04-01-2009, 10:10 PM
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Geessh, ask a simple question. The non-Perma Center All Americans were introduced in 1954 in 2.5X, 3x, 4x, and 6x. In 1957 8x and 10x were added. They were all designed to use the same parts, except for the lenses, this meant that click values varied from 1 moa in the 2.5x to about 1/4moa in the 10x. This is all according to Bob Bell in the Gun Digest Book of Scopes and Mounts. So your 4x would have a click value of about .625 (5/8) inch at 100 yards.
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  #6  
Old 04-02-2009, 01:24 AM
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Thanks for the suggestions and help fella's-very informative. LS
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  #7  
Old 04-02-2009, 01:26 AM
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PS: Madsenshooter, that was exactly the answer I was looking for,thanks-LS
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