If I buy a scope with a 50mm objective that is set to be parallax free at 100 yards, what is the maximum error due to parallax at 25, 50, 200, and 500 yards if the scope is set to x10 power (ignoring all other factors that can effect shot placement)?

I'm just guessing here , but my answer may spur someone with more knowledge on this subject to give us both the real answer.
25 yds. 3/16"
50 yds. 1/8"
75 yds. 1/16"
100 yds. 0"
200 yds. 1/4"
500 yds. 1"

Jackfish - Help!!!

I'm not sure that can be predicted in advance....

Wouldn't it be a function of how "off the center line" your eye lined up?

I just wanted to know how far my shots can potentially be off if I buy a fixed parallax scope. Lee - thanks for the info. If your approximations are fairly close, then that is the information I was lookign for. ntjaxn - I think you are correct, it depends how you look though the scope - which is why I asked for max error.

I'm not going to say that Lee is wrong... but.... with some scopes that are set to be parallax-free at 150 yards, I can see noticable parallax moving my head side to side at 100 yards. How much? I don't know, because I have no way to measure it. But it would appear to be at least several inches, if you move from exteme edge of the field of view to the other.

If you *really* want to eliminate this as a source of problems, get a scope with an adjustable objective. They really are worth it for target shooting and long range varmiting.

I don't have a data based answer, and I've never seen any such data published.
Just from my own experience of moving my head around behind various scopes over the years, and watching crosshairs move, I would guess parallax error is potentially a good deal larger than what LeeJ has posted.
I completely agree that an adjustable objective is the way to go in any high powered scope.

Again , I will say my estimations are merely guess-work. However , of all of the info I have read on the subject of parallax , every author has basically said the same thing , that being --- the amount that you are off due to parallax is probably smaller than your wobble in your hold. Also , about the only guys that will notice accuracy degradation due to parallax are top bench rest shooters. These are not my observatios but those of authorities on the subject. You just need to hold your eye as near center of the scope as possible , which you can see because the closer to center you are the rounder the image in your scope. I don't worry about parallax based on what these men have stated in print.
Have a good day people.

There are too many variables to do anything more than guess work. The guess work thus far has been lenient. These problems are actually noticable to far more than just bench resters, although for hunting big game it would not be as much an issue. Quality of the optical device is a big factor here as I have seen scopes that spray 8-12 inches because of severe parallax problems (an expensive Euro even). If true precision is the goal an adjustable optic would be an absolute must. If taking a 500 yard shot at a deer (IMHO it had better be wounded) you likely will still make the shot if you doped range and WIND correctly. Parallax is definately more of a problem than usually given credit for in both long and short range affairs.

Idoc

I agree with Lee that it is probably not going to be an issue for normal hunting, especially if the slightest care is used in getting your head lined up straight behind the scope.

But you did say 'maximum'....