Scope height vs Accuracy


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Mustanir
January 20, 2011, 02:06 PM
I wonder if someone could tutor me on the relationship between the accuracy and the height of scope.:scrutiny:

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kis2
January 20, 2011, 02:17 PM
the higher a scope is mounted, the farther away it is from the bore. when you shoot, if your rifle is at all canted, you can dump bullets to the left or right. this problem becomes more exaggerated 1.) over distance 2.) the greater distance between scope and bore

is that kind of what you were looking for? it's not that you can't have a high mounted scope and be very accurate with a rifle, but having the scope close to the barrel just makes things simpler.

Mustanir
January 20, 2011, 02:25 PM
So are you hinting that adding a cheek pad is all that can eliminate the difference between a high mounted scope and a low mounted scope?

jlg
January 20, 2011, 02:33 PM
The cheek pad will help you get better eye alignment without having to crane your neck.

If you're shooting deer within 300 yards you'll never know the difference. If you're shooting bullseyes at 1,000 yards you'll need to make sure the rifle is sitting level when you pull the trigger. The closer the centerline of the scope is to the centerline of the bore the less this will affect you.

This is much harder to explain without a picture.

Damon555
January 20, 2011, 02:43 PM
Scope height has absolutely nothing to do with accuracy.

That is unless it's so high that you need to crane your neck to look through it. But I've seen guys set up to shoot 1000+ yards with the scope wayyyy up there.

jmr40
January 20, 2011, 07:04 PM
Agreed, it has zero effect on accuracy. I prefer my scopes mounted as low as possible though because it makes it easier and quicker to pick up the target through the scope.

Offfhand
January 20, 2011, 07:05 PM
Read above what Damon555 had to say. That's all that needs to be said.

Heavies
January 20, 2011, 07:14 PM
Get one of these, keep things on an even keel.

http://i1000.photobucket.com/albums/af127/heaviescc/photo-7.jpg

BrocLuno
January 21, 2011, 12:16 AM
I agree, it's all about being repeatable in cheek weld and eye placement behind the ocular bell. You need a consistent sight picture. Big objective lenses (44mm and above) may pull you up off the stock to get centered. Adding a mole skin cheek pad will put you back behind the glass in the right place. There are a bunch of nice cheek pads out there. Pick what you need for your scope.

All scopes should be mounted as close to the barrel as they can, but 50's, 56's & 60's don't sit low, no matter what you do :(

kis2
January 21, 2011, 12:41 AM
let me clarify my point a little here: it's not really that scope height (both in canting and eye alignment) affects accuracy, but consistency. Mounting a scope low can help reduce the affects of canting (along with a level like in the picture above) allowing you to be more consistent and a cheekpad can help get weld consistency.

but it's not like a quality scope loses it's quality just because of its height.

bhk
January 21, 2011, 11:49 AM
You also need to keep in mind that a high-mounted scope will have more close-range offset that a low mounted one. This may not be an issue with a rifle intended to be used at long range or at large targets at medium to long range. It can be a significant issue for a rifle designed to shoot from very close to very far, such as tactical ARs. Folks shooting these rifles should be aware that their bullets may hit 2 or more inches low when shooting close up.

This can also be an issue with .22 rimfires because most of them are shot at very small targets at close up to medium ranges. This is why I want no part of a .22 AR. I don't want to be figuring the offset needed to shoot at a 7-yard squirrel's head when the rifle is sighted in at 50. It is tough enough with a low-mounted scope on a tradition rifle.

Another point is cheek weld. If you are shooting rifle with a traditionally styled stock, you will lose your cheek weld with a high-mounted optic. This weld is important in quick target aquisition and overall 'shootability' of a rifle. I generally mount my scopes as low as possible because I want the rifle to mount like the shotguns I use for quail hunting. If I mount my rifle with my eyes closed, I want to be looking straight through the scope when I open them.

A_Matthew
January 21, 2011, 12:03 PM
It has nothing to do with accuracy like the above posters said, but it can be handy for lengthening the range of your short range rifle. Lets say you set your scope 3" above the bore. Now, your bullet has to travel 3" higher to reach the crosshairs in your scope, thus lengthening your range by having the bullet travel higher, resulting in farther. It's really hard to explain, (typing it out, I mean) but my friends iPhone ballistic calculator proved the theory.
So raising your scope does not improve accuracy, it only lengthens the range. Hope this helps. Matthew

Mustanir
January 24, 2011, 01:39 PM
Which means that you are more accurate at longer range.
If we zero a center fire at 25 yards with low mounts than raise the hight of the scope by one inch will it shoot one inch higher?

jmr40
January 24, 2011, 01:45 PM
It still has nothing to do with accuracy. Most scopes are mounted about 1.5" above the bore. If you start shooting at extreme long range you will eventually run out of scope adjustment and can no longer zero at that range. Raising the scope a little higher will give you a bit more adjustmet.

Accuracy will be the same.

Byron
January 24, 2011, 01:52 PM
I have an old SP Colt AR.If the scope is mounted on top the carry handle/rear sight,and zeroed at 25 yards, approximately how high would be the impact at 100 and 200 yards? Thanks, Byron

A_Matthew
January 25, 2011, 01:52 AM
Originally posted by Mustanir
If we zero a center fire at 25 yards with low mounts than raise the hight of the scope by one inch will it shoot one inch higher?
It would then shoot one inch lower. To get it to shoot dead-on again, or one inch higher, you have to adjust your crosshairs.

Originally posted by Byron
I have an old SP Colt AR.If the scope is mounted on top the carry handle/rear sight,and zeroed at 25 yards, approximately how high would be the impact at 100 and 200 yards? Thanks, Byron

It should shoot within an inch or two of dead on at 100yds, and about 5" low at 200yds. Of course, a lot of it depends on your barrel length, weight of bullet, how "hot" the load is and a few other variables. Check out the ballistics tables over at RifleShooterMag.com, that's where I got most of my information.
Matthew

Haxby
January 25, 2011, 02:20 AM
"I have an old SP Colt AR.If the scope is mounted on top the carry handle/rear sight,and zeroed at 25 yards, approximately how high would be the impact at 100 and 200 yards? "

The sights on an AR are about 2.5" above the bore. Put a scope on top of the handle, it's maybe 4" above the bore. BC of .2, 3000fps, 25 yard zero. At 100 yards you're about 10" high, at 200 you're about 19" high. This according to Sierra's Infinity ballistics program.

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