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Parallax Testing

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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/20/2009 at 21:56
Sandracer View Drop Down
Optics Apprentice
Optics Apprentice

Joined: January/11/2009
Location: Eastern Oregon
Status: Offline
Points: 141
How much is acceptable in a 3-9 scope and how do you determine it? Just put a scope on  a new 22-250 to test the scope and couldn't group worth a crap at 30 yards unless I left it a 6x or less. I was trying to get it close at 30 before going out farther. There was over 2" difference from my POI at 30 yards from 6 to 9 power. Then I noticed if I moved my head just a little while on the rest the cross hairs went all over the place. If this is normal I guess I've nver noticed it before! Too much snow to get out farther at this point.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/21/2009 at 09:50
John Barsness View Drop Down
Optics Optimist
Optics Optimist

Joined: January/27/2009
Status: Offline
Points: 785
That is pretty much normal for a 3-9x at 30 yards. Unless the scope has some means of parallax adjustment, such as an adjustable objective or side-focus (and few 3-9x scopes have either) there will be considerable parallax at close range, because most 3-9x hunting scopes are set to be parallax-free at 150 to 200 yards.
You determine how much parallax there is in a scope at a certain range by putting the rifle on rests, and either hold it very steady or balance it so you don't even have to hold it. Then you move your eye around behind the scope and observe how much the reticle "moves" across the target.
BUT, there is NO parallax at any range IF your eye is perfectly lined up behind the reticle. This is why when shooting at closer ranges, I try to center my eye behind the scope. This is most easily done by moving your eye back far enough from the ocular (rear) lens that you don't see the entire field of view. Instead you see a bright circle within a black outer ring. Center the bright circle in the dark ring, and parallax will be pretty close to non-existent.
Also, parallax is also normally less at lower magnifications in a variable scope. If you set the scope on 3x (plenty for shooting at 30 yards) then parallax will normally be much less than at 6x.
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