Why does the reticle move when I change the magnification?

[Wolfdawg]

While setting up my rifle to shoot a recent 1000 yard match, I put the crosshair on the target. I then turned up the magnification and the crosshair moved on the target pretty significantly. It seemed to moved its point of aim vertically.

WHY???

Shouldn't the crosshair stay on the target regardless of the magnification?

Wolfdawg

 

[M-61]

Yes it should.
And you said vertically....so we are not talking about FFP scope where the reticle increases in size (overall) as the power is cranked up.
Some scopes I have, increasing the power while looking at the target is not so easy as the power knob does not turn freely so the scope moves, not staying still on the target. Not a complaint just an observation.

 

[Ledd Slinger]

What scope is it? Cheap scopes are notorious for that problem.

 

[M-61]

What scope is it? Cheap scopes are notorious for that problem.

Should have been my first question!
Ledd you are 100% correct on the cheaper scopes.

 

[Wolfdawg]

I have 3 NightForce BR scopes. 12-42 and one 8-32.

When competing at 1000 yard BR matches, I noticed that if I set the crosshairs on a point at the back bank, for example, and then change the magnification, the aiming point moves considerably. When I turn the magnification back, the aiming point goes back to the original point.

BUT, why???? The reticle size does not change on the NF BR scope when magnification changes. These are top end scopes, nothing "cheap" about them. They are used by just about ever 1000 yards competitor that I know.

There has to be some scientific reason for this. Try it the next time your at the range. Only change the mani fixation when the rifle is totally locked in and watch the reticle.

Wolfdawg

 

[dkhunt14]

It should only do it if you are not using the middle crosshair or aiming point. Matt

 

[Ledd Slinger]

I have 3 NightForce BR scopes. 12-42 and one 8-32.

When competing at 1000 yard BR matches, I noticed that if I set the crosshairs on a point at the back bank, for example, and then change the magnification, the aiming point moves considerably. When I turn the magnification back, the aiming point goes back to the original point.

BUT, why???? The reticle size does not change on the NF BR scope when magnification changes. These are top end scopes, nothing "cheap" about them. They are used by just about ever 1000 yards competitor that I know.

There has to be some scientific reason for this. Try it the next time your at the range. Only change the mani fixation when the rifle is totally locked in and watch the reticle.

Wolfdawg

Thats not supposed to happen. Moving the reticle in any way changes POI. To check and make sure it's not your eyes or the atmosphere playing tricks on you, fire a 3 shot group at 500 yards or further (1K if you can) with the scope on 12X or whatever lower setting that you see the reticle shift. Then another group with it on 42X. If the POI has changed along with the reticle movement, I'd call NightForce and ask them to fix it. Wouldn't think NF would have trouble with that, but you never know...

I'm no expert, but when I research new brands and models of scopes to purchase there's a few things in reviews I look for. One is optical quality and how much light, resolution, and eye relief a scope loses on max power setting. Two, abuse tests for holding zero. Three, verifying adjustments are repeatable by conducting box tests with groups (not single shots). Finally, if the scope maintains same POI throughout the magnification range. All very important.

 

[M-61]

Quote from Wolfdawg:
"BUT, why???? The reticle size does not change on the NF BR scope when magnification changes."

This is a second focal plane scope. The reticle does NOT increase in size when increasing magnification as in a first focal plane.
Ledd Slinger's response is correct regarding POI.

 

[dkhunt14]

If you have reticle like the NPR2 and you don't use the middle crosshair the image will move as you turn the power up or down. Only the center will stay centered. As the magnification increases so does the size of the target you are looking at. The farther away or the more magnification the farther the crosshair will move off. Set your gun up at distance with the crosshair (not the middle) on an object and crank the power up and you will see. That is why one power setting on your scope is marked with an R. It is between 20 and 26 on the 12x42. If you use any power other then the R the MOA for ranging or holdover will be off. Matt

 

[GrocMax]

What about parallax?

 

[M-61]

What about parallax?

A pretty good explanation in understanding parallax:

http://www.snipercountry.com/Articles/Parallax.asp

 

[Ledd Slinger]

What about parallax?

I would assume a 1K BR shooter knows how to adjust parallax, but that is a very good point in question. Improperly adjusted parallax will most definitely move the reticle around.

 

[M-61]

What about parallax?

I would assume a 1K BR shooter knows how to adjust parallax, but that is a very good point in question. Improperly adjusted parallax will most definitely move the reticle around.

I was replying to GrocMax who I did not know was a 1k shooter.
I think it is a well written article clearly answering many questions regarding parallax. Overall worth reading. This is strictly my opinion

 

[Ledd Slinger]

What about parallax?

I would assume a 1K BR shooter knows how to adjust parallax, but that is a very good point in question. Improperly adjusted parallax will most definitely move the reticle around.

I was replying to GrocMax who I did not know was a 1k shooter.
I think it is a well written article clearly answering many questions regarding parallax. Overall worth reading. This is strictly my opinion

I wasnt referring to you at all M-61..I quoted the reply from GrocMax.

I was just showing agreement with GrocMax that Wolfdawg may have his parallax out of adjustment. Even the most experienced folks can overlook the simplest of things from time to time.

 

[M-61]

Understood Ledd Slinger......and you are 100% on the money (again) with your last sentence!

 

[GrocMax]

No I'm not a 1K shooter, but it occurs to me its about impossible to dial up/down your magnification AND dial in correct parallax/'side focus' at the same time, and some scopes may need an adjustment between 500 and 1000 yds, and the 'infinity' stop and not quite to the stop may be an in-betweener at the yardage observed.

 

[dkhunt14]

Nightforce BR Scopes do not have side focus, it is up front on the objective lens. Parallax will move the crosshair both ways not just vertical. It all depends upon where your head is in relation to the crosshair. Parallax usually doesn't move the crosshair very much. If you are that far out the scope will be out of focus. He also said it moves vertically and a substantial amount. Matt

 

[sscoyote]

Go right out and purchase a magnetic grid boresighter, stick it on your muzzle and check reticle shift with both magnification changes and power changes. Tell you lickety split wether your scope has problems or not, and by how much MOA.

 

[Dusty Stevens]

Wait til winter mike.

 

[M-61]

gunsandgunsmithing quote:
"I hope it's short and mild!
This site has changed a lot of late."

To your 1st sentence Me too
To your 2nd sentence It sure has