I just picked up a beautiful old 308 Norma on a '03 action, topped with a Leupold 3x9. After a run to the range I knew it had a problem ...scattering shots into about a 4" group roughly centered on my point of aim. I brought the rifle back, put it on three power and set it in a cradle facing a piece of furniture with a checked pattern covering. When I looked through the scope and moved my eye slightly, the center of the crosshairs circled the target point in opposition to my eye movement. If I moved my eye to 4 0'clock, the center of the crosshairs moved to 10 o'clock. I tried another of my scopes and this didn't happen. To me, this is parallax. I am, however, a vivtim of my training. In "Theory of Tank Gun Accuracy" classes at the Armor School at Fort Knox, I was taught the definitions of two commonly used terms that don't exactly jive with how we use them in sporting terms. The first was "head-space" and the other was "parallax". Is what I'm seeing what everyone else knows as parallax?

Yes sir Col K... That would be parallax.. With several scopes I have noticed that this phenomenon can happen if you are outside of the "comfort" zone of the scopes eye relief as well....

Ken....

Hey Col K

One little trick that will help you deal with that parallax is to mount the scope a little far forward than you normally would. When you get down on the scope a black circle will appear around the edges. Normally you mount your scope far enough back to get rid of this circle. Center the black circle around the edges and you have aligned your eye with the reticle and target and parallax is no longer an issue.

The parallax on the 3X9 is usually adjusted for 150 yds, and if you were viewing an object at less or more than that, you'll see some parallax (greatly exaggerated at close range). Leupold can adjust that to whatever distance you specify -- although I don't believe it is covered under warranty. I think the charge I was quoted was $25 or so for a VariX II 2 X 7. If you are adventurous and wish to try it yourself, here's a website with instructions:

http://www.charm.net/~kmarsh/adjust.html

I followed the instructions and adjusted my Leupy 2X7 to 40 yds to use on a .22 for squirrel hunting and it was easy, once I got the lock ring loose.

quote:

I brought the rifle back, put it on three power and set it in a cradle facing a piece of furniture with a checked pattern covering.

Yes, that is parallax, and at the range of say, 20 feet, it is extremely apparent.

However, if you'll do the same test at 100 yards you'll find virtually no parallax error(assuming that the scope was properly adjusted for the standard 150 yard parallax-free range). Your 100 yard groups might conceivably suffer by a half inch with the most extreme change in eye placement, but you'll have to look elsewhere to explain 4" groups.

quote:

Originally posted by dustoffer:
I followed the instructions and adjusted my Leupy 2X7 to 40 yds to use on a .22 for squirrel hunting and it was easy, once I got the lock ring loose.

So does this adjusting let the gas out and air in?

I noticed an optical restorer adjusted a scope of mine to 100 yards (4x fixed). Don't know why, but it would tend to suit me anyway. I think.

The rifle scopes are usually set at 150 yds and the shotgun scopes at 75 yds .I use a 75 yd parallax for my 45-70 since I hunt at close range. Leupold will change parallax or cross hairs for a small charge.