Sight picture question (I think)?

[JT]

I have a Vortex Viper on my AR10, and I seem to have a lot of trouble with my sight picture. I have to get so far down on the stock that my glasses are pressing into it, and when I go to the scope I have to do a lot of fore-and-aft to get the sight picture. And all this is at minimum zoom. When I crank it up, I'm looking all over the place to acquire a decent sight picture.

As I've said elsewhere, I'm relatively new to optics (having been an irons man for almost sixty years) and I honestly don't know if this is a problem with the scope, its position on the rail, the lack of drop on the stock comb, my inexperience, or some factor of which I haven't even yet thought.

Have I given enough information for a diagnosis? I'd really appreciate some help. Understand now that I can get a sight picture -- it just seems like I'm having to work too hard and make too many adjustments with this particular setup. By comparison, I have no problem at all acquiring a quick picture on the red dot on my PCC or the Strike Eagle on my AR15.

TIA for any help!!!

 

[JimP42]

Use the rings that put your eye in line with the scope with a comfortable repeatable cheek weld. Build up the stock of the scope objective is too large but it doesn’t sound like that is your problem. Adjustable comb makes this easier.

Once you have the scope at eye height, adjust the scope fore/aft while loose in the rings to the middle of the range that works for your sight picture. Then torque properly.

You should be able to put your head on the rifle and the sight picture is right there, every time. At least for a particular position. Standing vs bench vs prone may affect it so pick the one most important to you or try them all to figure out which placement is the best compromise and learn the cheek weld for each position.


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[Catfish]

 

[Get Off My Lawn]

A Magpul PRS (cheek height adjustment) made a huge difference for me with a high power scope.

 

[JBoyette]

Ok so the issue is eye relief and optic mount height. Without knowing your mount system it can be too high or too low. Need a picture to tell. I would say by your description the optic mount its too low.

The back and forth is based on the eye relief measurement of the optic. if you could, post a picture of the rifle with the optic mounted so I can look at your situation and give you the best advice.

We can fix this, no issue.

One fun thing to do.

You will need:
a flashlight
a measuring ruler
an index card
a second set of hands or a gun rest.

1. Take the optic and bump it to max magnification.
2. at 1" from the objective turn on the flashlight and shine through the riflescope lens
3. with the index card place it at the end of the optic and move the card back and forth until you go from a donut to the tightest solid ball of light.
3.a measure this distance from the rear of the optic
4. Bump the magnification down to its lowest setting
5-6a repeat steps 2,3,3a

At the end, you now have the measurement range +/- where your eye must be away from the optic. I would lean towards the max ball of light measurement.

The location of your eye is a mixture of length of pull of the stock X-axis and trigger location Y-axis to your comfort.

I always take duct tape and a BB and when I get behind a rifle and get it to fit me I place that duct tape so the BB hits my cheek and I can repeat this spot. The optic will move away from my eye, to be placed at the right X-axis away from me to the measurement of step 3.a and 6.a. The height is based on the proper optic mount, typically for me "and most everyone else" the height for centerline of the optic is 1.5" above the rail.

 

[REELDOC]

What he said about the 1 1/2" ^. Shoulder the rifle in the position you think you will most use the rifle. Then, simply lay yer noggin on the stock without mashing it in. I normally set my stuff for a prone/bench position so when I shoot high recoiling stuff I don't take the chance of crawling up on the stock.

It is better to have the mount height a little too high than too low. Easy to build up the stock or get an adjustable height cheek piece for proper cheek weld.

 

[NKD]

Might have a look at 1.93” mounts.
Regular AR mounts always feel a bit low to me.

 

[BowWow]

I have a Vortex Viper on my AR10, and I seem to have a lot of trouble with my sight picture. I have to get so far down on the stock that my glasses are pressing into it, and when I go to the scope I have to do a lot of fore-and-aft to get the sight picture. And all this is at minimum zoom. When I crank it up, I'm looking all over the place to acquire a decent sight picture.

As I've said elsewhere, I'm relatively new to optics (having been an irons man for almost sixty years) and I honestly don't know if this is a problem with the scope, its position on the rail, the lack of drop on the stock comb, my inexperience, or some factor of which I haven't even yet thought.

Have I given enough information for a diagnosis? I'd really appreciate some help. Understand now that I can get a sight picture -- it just seems like I'm having to work too hard and make too many adjustments with this particular setup. By comparison, I have no problem at all acquiring a quick picture on the red dot on my PCC or the Strike Eagle on my AR15.

TIA for any help!!!

The posted video pretty much covers it. It sounds like you need some higher scope rings or mount.

One thing I will add it a term called "Exit Pupil"... you will see this on the specs of the scope. This refers to a diameter size of which the image from the scope can be seen...… with a higher magnification and smaller diameter lenses, you will have a small exit pupil - say 2mm. This means your eye will have to be aligned within a 2mm area to get a clear image from the scope. You will need a fairly consistent cheek weld. With lower magnification and larger diameter lenses, its more forgiving....you might have a 10mm exit pupil. Now you have a much larger spot to align your eye to. With a variable power scope, the exit pupil varies with what you have your magnification set at.

And referring to the video, the section about focusing the reticle. Do that first before you mount it. Go outside and look through the scope into the sky on a clear day.... this makes a really crisp image to set your reticle focus.

 

[BatteryOaksBilly]

Ok so the issue is eye relief and optic mount height. Without knowing your mount system it can be too high or too low. Need a picture to tell. I would say by your description the optic mount its too low.

The back and forth is based on the eye relief measurement of the optic. if you could, post a picture of the rifle with the optic mounted so I can look at your situation and give you the best advice.

We can fix this, no issue.

One fun thing to do.

You will need:
a flashlight
a measuring ruler
an index card
a second set of hands or a gun rest.

1. Take the optic and bump it to max magnification.
2. at 1" from the objective turn on the flashlight and shine through the riflescope lens
3. with the index card place it at the end of the optic and move the card back and forth until you go from a donut to the tightest solid ball of light.
3.a measure this distance from the rear of the optic
4. Bump the magnification down to its lowest setting
5-6a repeat steps 2,3,3a

At the end, you now have the measurement range +/- where your eye must be away from the optic. I would lean towards the max ball of light measurement.

The location of your eye is a mixture of length of pull of the stock X-axis and trigger location Y-axis to your comfort.

I always take duct tape and a BB and when I get behind a rifle and get it to fit me I place that duct tape so the BB hits my cheek and I can repeat this spot. The optic will move away from my eye, to be placed at the right X-axis away from me to the measurement of step 3.a and 6.a. The height is based on the proper optic mount, typically for me "and most everyone else" the height for centerline of the optic is 1.5" above the rail.

LIKE!!!!!!!!!!!!!