Scope performance?

[stinkycat]

I was having a discussing with my Nephew about rifle scopes and eye placement. I have always thought that when one rifle/scope is sighted in for one person that it may not be for others ...... depending on how you hold the rifle and where your eye is located in respect to the scope. My nephew is under the idea that it does not make any difference. He also thinks this issue is the same with red dot type scopes as well as traditional.

What do you guys think?

[wallymn99]

IMO it doesn't make a difference. I have shot many rifles that aren't my own and the groups have always been consistent from a bench rest. I have had rifles sighted in for me, that work well too. I think it would depend more on how your eyes are compared to someone elses eyes rather than the scope.

[T Mac]

If the scope is on ...it is on.
But, a person for whom the scope is not fitted may issues with eye relief.
If he can't get a clear, full scope view, he will have to get his eye closer or further from the scope, until he can. In other words he'll have problems seeing the target and full view in a comfortable position.
This results in movement and inconsistent shooting.

[REG]

Scopes are set to be parallax free at a given distance - most are 100yrds. If you were to put your rifle into some sort of holder so the rifle can't move and then while looking through the scope - move your eye around (so the crosshairs are not centered in the eyepiece) - you'll notice that the crosshairs actually stay on the same spot on the target - no matter where you put your eye. (provided the target is out at 100yrds or farther) This way anyone should be able to situate their eye however they like (within reason) and the rifle will still be on target.

Red dots are usually noted to be parallax free.

I've always heard that when two people shoot the same firearm to two different points of aim, it's usually because of differences in how they pull the trigger. Especially with pistols.

[yarcraft91]

It is possible that a scope not properly adjusted (or incapable of this adjustment) will have a reticle that "moves" compared to the scope image (or vice-versa) when you move your eye back-and-forth or up-and-down (parallax error). In that case, different eye positions relative to the scope can cause 2 people to have a different point of impact for the same point of aim.

Here's an article on the subject.
http://www.snipercountry.com/Articles/Parallax.asp

[Nick Kanauz]

Yep...if the rifle is bore sighted properly, and then the scope is zero'd at the 100 yd mark, it will stay at that mark. If someone else shoots the rifle, the only way it is off is indeed trigger pull. If you are shooting your rifle properly, you should actually see the round hit the target area. Also...when I occassionally sight in for friends...I have them reset (practice) cheek placement on the stock to make sure their field of view is consistent. I also make sure they know that I have sighted in the scope to be dead center, 1" high at a 100 yds. This will ensure a dead on 200 yard shot. Of course, this changes by caliber, grain, and downrange bullet velocity. Most of the time though an inch is good. The only time there will be a problem is if a right handed shooter is left eye dominant...then the impact spot will be right, left, or up/down from the sighted spot. Left eye dominant shooters will have a different aim point than right eyed, right handed shooters, and vice versa. Hope this helps.

[Noah Cantell]

Length of pull, etc. can make a diff ? Different size folks hold the firearm different ? I think so. What say all of you ?

[Esoxchaser]

To put it in it's simplest terms, the scopes function is to simply mark the point where the bullet will impact at a given yardage. The scope will always point to the same spot, regardless of who is looking through it. Who pulls the trigger should be irrelevant. The problem is that many shooters don't practice enough, and can't manage to pull the trigger without moving where the gun, and scope is pointing.

[2Labs]

To put it in it's simplest terms, the scopes function is to simply mark the point where the bullet will impact at a given yardage. The scope will always point to the same spot, regardless of who is looking through it.


Yup. Been shooting for 50+ years now, 40+ with scopes. A different shooter will NOT require a change in the crosshair setting. Point of impact will NOT change.

What MIGHT change is the new shooter may need to creep forward/backward with their face on the stock to see the crosshairs in full.

What MIGHT happen IN EXTREMELY RARE occasions is the new shooter may need to change the FOCUS of the eye piece by turning it in or out (the eye piece screws into the scope from the back). BUT, even that will NOT change point of impact of the bullet because it does not change the settings of the crosshairs. Just reverse the change the new shooter made so the focus is back where you want it and you will be fine. I should also point out I have only seen this focal adjustment needed once in my 40+ years of shooting scoped rifles.

[Waxy]

I completely agree with most here that in theory, once the scope is zeroed on the target for a given range, the point of impact shouldn't change regardless of who's shooting the gun and for the most part, I've found this to be true. I regularly sight in rifles for other people with no issues.

However, I have come across a few situations over the years where it simply was not the case, and I'm not talking small differences either, I'm talking differences of up to 6" or more at 100yds. It wasn't related to poor shooting skills by one of the shooters either, because when left to zero in the rifle on their own, each was able to consistently fire very accurate groups. The only variable was the person shooting, and the way they held and fired the rifle. It was pretty baffling, but undeniable.

I'm sure some will say it's not true or due to some other factor, but personal experience would lead me to believe that how an individual holds and fires a rifle can and does have an affect on the point of impact.

Waxy

[Phil T]

If your scope is zeroed for you, it may actually not be zeroed for someone else, especially if they differ from your body build. The reason is recoil.
Using a 30-06 as an example, the rifle has moved about 3/8" by the time the bullet has left the muzzle. If the other person is lighter than you, it will have moved (usually upward and maybe to the right with a right-handed shooter) more than when you shot it. Believe it or not, even the pressure on the stock by the person's cheek will effect the bullet impact a little. How firmly the shooter pulls the rifle into his shoulder has a much greater effect.
All this means that the sights must be adjusted for the individual shooter. I learned these things while on a college rifle team.
If you only check the sight adjustments with a bench rest and sandbags, the differences will be less. When hand held, the differences will be more noticeable. By the way, if the rifle has any recoil worth mentioning, the bullet impact will likely differ between resting on sand bags and hand holding. In my case, my 30-06 shoots 3" higher off firm sand bags than when I "position" shoot it. My 338WM differs by 6" at 100 yards. I changed to a soft rest on the bench after I learned that.