# Effect of scope height on performance



## THE JAMMER (Aug 1, 2005)

Ok we got 72 hits on my last subject: 40 S&W vs. 45 ACP, and I promised Charlie a new one. So let's try this one. What is the effect on gun performance if I increase the height of the scope above the bore? Does it make the gun shoot flatter? 

This should be a good one. I will hold my opinion until we get some responses.


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## Ernest (May 21, 2004)

You failed to define shoot flatter. 

That said, the external ballistics are determined by the round and the barrel. Its all about velocity and BC. Not hand guards, scopes, or lasers. 

Where you mount the scope - high rings vs. low rings - changes where the barrel might point, but it never changes velocity or BC. Or gravity or wind. 

The effect of vertical angles (gravity not perpendicular to the path of the bullet) exists irrespective of scope height. Thus, scope height cannot accurately be described as making any of the changes in bullet path associated with vertical angles. Its sole cause is the non perpendicular angle of gravity, and it would exist even if no scope or sights were present. 

So, short answer, NO. 

Effect on gun performance? Not sure if that is even a serious question. The impact of scope height is well known, well documented, and exhaustively researched. It simply changes the angle of line of sight/aim to the bore axis.


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## CHARLIE (Jun 2, 2004)

Nope it doesent make the "gun" shoot flatter nor does it effect gun performance.


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## Trouthunter (Dec 18, 1998)

What they said and what took you so long to get us a new subject? 

TH


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## THE JAMMER (Aug 1, 2005)

Ok here is my take. Ernest jumped right on it in his first line. What does shoot flatter mean. Flatter relative to the barrel, or flatter relative to the horizon?? First of all I think all agree that the flight of the bullet relative to the extended axis of the barrel stays the same. I will often have people say, "A bullet starts dropping as soon as it leaves the barrel." Wrong. Do you mean if I point this gun up in the air and shoot, that the bullet is going to fall on the floor? Of course not. It starts dropping relative to the extended axis of the barrel.

Now with a higher scope mount here are two facts: your line of sight through the scope to your poi stays the same. However, the angle between the extended axis of the barrel to the line of sight is greater, because the bbl is lower. Therefore, let's say you have your gun sighted in 3" high at 100 yards- the bullet is still climbing when it hits 100 yards. If your scope is mounted higher, it's my contention that the bullet is climbing at a faster rate, and it will take a longer distance for it to fall back to line of sight. So relative to the ground, does that make it flatter shooting.

Now with the scope mounted higher, the disparities above line of sight at various distances will be greater than they would be if it were mounted lower. I.E. mounted lower, and sighted in 3" high at 100 yards, will probably be right dead on at about 250-275 yards depending upon caliber and velocity. whereas if the scope is mounted higher, and sighted in 3" high at 100 yards, the bullet will not fall back to line of sight until some distance past that 250-275 yards. So depending upon how far above los the bullet is at say 150, 200 yards etc. you might be able to hold dead on at a longer distance.

There is a reason that scope height is one of the inputs on every computer program.

What say you????


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## jimk (May 28, 2004)

Not flatter. Up to a point, the higher scope will have the 2nd line-of-sight intersection with the trajectory farther than that of a lower scope. Keep raising the height of the scope and the 2nd intersection starts decreasing while the 1st increases until you're looking at a single tangent point on the curve. It's important to every shooter and program.

Question: If the effects of gravity isn't instantaneous(no matter where barrel is pointed), when does it start?


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## Bottomsup (Jul 12, 2006)

If the bore is level to the ground the bullet does start dropping when it leaves the bore. The sights are not on the side of the barrel so this doesnt matter unless you shoot gangsta style. Most sights are above the bore so the two must intersect at some range or the rifle will always be shooting low. Since you cant change your line of sight the bore must be canted upward to intersect the line of sight at your desired distance.


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## Bottomsup (Jul 12, 2006)

Gravity pulls on the bullet no matter what angle it is shot at even straight up. It doesn't mean the bullet wont continue to rise but at some point gravity will overcome the inertia of the bullet even though its gradual.


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## Bass-Tracker (Dec 23, 2013)

Ernest said:


> So, short answer, NO.
> 
> Effect on gun performance? Not sure if that is even a serious question. The impact of scope height is well known, well documented, and exhaustively researched. It simply changes the angle of line of sight/aim to the bore axis.


Scope height has nothing to do with how the rifle shoots.
Only difference is angle of the bullet path & the zeroing of the scope.
Soooooooo simple.

.


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## CHARLIE (Jun 2, 2004)

What say you ? Well I say this Jammer, I think you answered your question very well in your 2nd post. LOL. Remember we are talking about maybe 1/4 inch between low and hi mount so are we getting away from being practical ? Next question ??


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## deckh (Jul 23, 2010)

LOL. The Jammer asks a question or makes a proposal and then answers his own question. Kinda reminds me of Bill O'Reilly asking someone a question during an interview and then interrupting to answer his own question. Very entertaining!


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## THE JAMMER (Aug 1, 2005)

Bottomsup said:


> If the bore is level to the ground the bullet does start dropping when it leaves the bore. The sights are not on the side of the barrel so this doesnt matter unless you shoot gangsta style. Most sights are above the bore so the two must intersect at some range or the rifle will always be shooting low. Since you cant change your line of sight the bore must be canted upward to intersect the line of sight at your desired distance.


Agree.


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## THE JAMMER (Aug 1, 2005)

Bottomsup said:


> Gravity pulls on the bullet no matter what angle it is shot at even straight up. It doesn't mean the bullet wont continue to rise but at some point gravity will overcome the inertia of the bullet even though its gradual.


The only instance in which this would not be true is if you shot the bullet absolutely straight up (with no wind), in which case the bullet would travel parallel to the extended axis of the barrel until it ran out of speed.


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## CHARLIE (Jun 2, 2004)

And Jam why does it run out of speed ??


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## THE JAMMER (Aug 1, 2005)

deckh said:


> LOL. The Jammer asks a question or makes a proposal and then answers his own question. Kinda reminds me of Bill O'Reilly asking someone a question during an interview and then interrupting to answer his own question. Very entertaining!


LOL all you want deckh. One of the main reason I am on this forum is to learn more about one of my major hobbies from the incredible people who are on it. Am I not entitled to my own opinion on a subject that I put out to the forum for their expert inputs?? I sure hope so. I, and a lot of the others on here, enjoy expressing their opinions and sharing information, and if my putting out a subject for discussion enables me and others to learn more about it (myself included), I think that is good. For instance when I put this out I could not wait for inputs from people like Ernest and Charlie on it. Guys like them have so much experience and knowledge, I want to soak up as much of it as I can.

By the way I watch O'Reilly every night, and I totally agree with your assessment of how he has become so "my way or the highway." I realize he has time restraints and sometimes has to cut filibuster, but sometimes I too wonder "why did he bring the person on the show anyway," if all he is going to do is overspeak them. I really don't think you can compare my putting out a subject, reading and learning from everyone's inputs, and then expressing my own opinion as well, to what O'Reilly does. You have every right and opportunity to express your thoughts on the subject. I cannot cut you off like O'Reilly can. By the way- do you have any inputs or thoughts on this?? You are certainly welcome.


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## CHARLIE (Jun 2, 2004)

Hey Jam thanks for the input. I will say this, Ernest has the technical input (at least it appears that way to me). I dont always agree with his accessments of things. But now me I have only old age and exerience to fall back on. Sometimes that aint all bad. Dont worry about deckh I think he certainly wasnt being serious or trying to condem anyone. Keep up the good work.

Oh yeah i watch Oreilly too.


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## THE JAMMER (Aug 1, 2005)

CHARLIE said:


> And Jam why does it run out of speed ??


Gravity pull.


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## CHARLIE (Jun 2, 2004)

THE JAMMER said:


> The only instance in which this would not be true is if you shot the bullet absolutely straight up (with no wind), in which case the bullet would travel parallel to the extended axis of the barrel until it ran out of speed.


Well maybe I misread your quote Jam. I thought it was referring to gravity but I may have mis read it.


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## THE JAMMER (Aug 1, 2005)

I just ran some numbers through a program I have: Assumptions: 30-06 180 gr bullet, bc .463, muzzle velocity 2700 fps

Scope 1" above bore:

50 yds 1.93" high
100 yds 3.64" high
150 yds 3.95" high
200 yds 2.81" high
250 yrd dead on
300 yds 4.46" low

scope 2.75" above bore (the scope on my colt AR is 2.75" above bore)

50 yds 1.06" high
100 yds 3.67" high I kept the 100 yard poi the same as above for comparison
150 yds 4.89" high
200 yds 4.63" high
250 yds 2.77" high
290 yds dead on
335 yds 4.44" low same distance low the above is at 300 yes

So obviously there are different POI's at the various distances. Now for practicality for a sniper- significant. For most of us shooting a whitetail in Texas- insignificant. Would I practically speaking sight my gun, that had a scope 2.75" high, to be 3.67" high at 100 yards? Probably not, because with that being 4.89" high at 150 yards, that could be a bad hit at 150 yards. Being 4.63" high at 200 yards- that could also be a bad hit.

However I could take that gun with the scope 2.75" high, and sight it in to be dead on at 250 yards and have the following data:

50 yds .53" high
100 yds 2.61" high
150 yds 3.29" high
200 yds 2.45" high
250 yds .11" high essentially dead on
300 yds -4.03" low

Those are all acceptable distances (except maybe for the 300 yd and the 150 yd shots) away from dead center for good kills by aiming dead on all the way out to 300 yards.

Everyone who has commented on this thread obviously knows what they are talking about, but I will guarantee you there are others who have read it, not commented, but have learned something.


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## DCAVA (Aug 5, 2013)

I have (2) .270's Remmy's 700 ADL's, both sighted in w/130 grain cores-lokt psp zeroed dead on @ 100yds; I have made several kill shots out to 250 yards w/either gun, and the bullet impact is dead on @ that range as well. Both guns are dead on up to 250 yards,but, I have not taken them to the range to see what the poi is past that distance. Don't really have time to kill @ the range, wish I did though, the good thing is peace of mind knowing no holdover is necessary to this range.

Yes Jammer, a great informative thread.....


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## THE JAMMER (Aug 1, 2005)

DCAVA said:


> I have (2) .270's Remmy's 700 ADL's, both sighted in w/130 grain cores-lokt psp zeroed dead on @ 100yds; I have made several kill shots out to 250 yards w/either gun, and the bullet impact is dead on @ that range as well. Both guns are dead on up to 250 yards,but, I have not taken them to the range to see what the poi is past that distance. Don't really have time to kill @ the range, wish I did though, the good thing is peace of mind knowing no holdover is necessary to this range.
> 
> Yes Jammer, a great informative thread.....


DCAVA, I hope that is true, but I am really having trouble understanding: dead on at 100 yards and dead on at 250 yds?? Seems almost ballistically impossible.

The only way I can get a sample 130 gr 270 core lokt with a bc of .336 (right off remington's website) and muzzle velocity of 3060 to be dead on at 100 and 250 is for your scope to be 5.94" above your bore. If that's where it is, that will work. Doubt it is that high.

If the scope is 2.5" above bore (more likely or less), and you are dead on at 100, you should be about 5" low at 250. Now with it like that, one might well could get a "kill shot" at the range (5" low might still be in the boiler room), but to say it is also dead on at 250 might be a stretch.

I just remember the old gauge my grandfather always gave me: on a normal deer cartridge in the approx 2700 fps mv, if you are about 3" high at 100, you should be dead on at about 250-275. That really seems to hold pretty true, plus or minus a negligible %.

These computer programs are amazing. The one I am using on my iPhone is "ifly". I think it's free, and very simple to use. I know I'm sick, but I have spent many evenings just playing "what if" games on that thing for hours. You can really learn a lot from them.


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## DCAVA (Aug 5, 2013)

THE JAMMER said:


> DCAVA, I hope that is true, but I am really having trouble understanding: dead on at 100 yards and dead on at 250 yds?? Seems almost ballistically impossible.
> 
> The only way I can get a sample 130 gr 270 core lokt with a bc of .336 (right off remington's website) and muzzle velocity of 3060 to be dead on at 100 and 250 is for your scope to be 5.94" above your bore. If that's where it is, that will work. Doubt it is that high.
> 
> ...


Ur prolly right Jammer, there has had to have been some variation to bullet impact on the deer shot I'm sure, I guess my meaning of dead on is buck in the dirt...

Like I say, I don't have a chance to get out and "practice" with my rifles, just depend on them to hold their zero, with proper handling ofcourse, and deliver at the moment of truth on game animals.

One of those .270's I sighted in, in 2000 with the 130grain core-lokt psp, and still use the same grain and brand of ammo and haven't had to adjust the scope at all over all these years, believe it or not.


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## jimk (May 28, 2004)

I'm using a Federal 130 grain Sierra BTSP(Game King) in a 24" barrel .270 with MV of 3,060 fps. If I'm dead on @ 100 yards I'm also 5" low @ 260 yards. Hard to argue with "buck in dirt."


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## CHARLIE (Jun 2, 2004)

Jam

Back on your comparison quote seems to me that you used two different calibers for a comparison. That aint gonna work.


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## CHARLIE (Jun 2, 2004)

Jam

Sorry my bad, I did not read your post cocrrectly just screwed up on what you actually said. Just comparison of the sight on your AR and not the caliber. Sorry..


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## B-Money (May 2, 2005)

If it is too high, it won't fit in the window of a deer blind.


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## CoastalOutfitters (Aug 20, 2004)

here may be a real world answer

IF, the center-line of the scope is exactly parallel to the center-line of the bore

one would expect normal scope bases to not make any diffrence

now take this to an extreme..........remembering chamber center to scope eyepiece center point A = barrel center to scope objective center point B

as you increase height of A and raise internal scope elevation for trajectory, I could see some difference between a std. mount and some extreme high mount , all else being equal.


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## deckh (Jul 23, 2010)

Jammer, Charlie and Ernest are correct in their response. Again, somewhat entertaining. How many angels can dance on the head of a pin??? Jammer, no harm, no foul.


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## THE JAMMER (Aug 1, 2005)

Bobby Miller said:


> If it is too high, it won't fit in the window of a deer blind.


Magnum LMAO on that one Bobby.


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## THE JAMMER (Aug 1, 2005)

deckh said:


> Jammer, Charlie and Ernest are correct in their response. Again, somewhat entertaining. How many angels can dance on the head of a pin??? Jammer, no harm, no foul.


Deckh, no worries for sure. Just trying to learn when I can, and to help when I can. this has been a pretty good one.


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## THE JAMMER (Aug 1, 2005)

CoastalOutfitters said:


> here may be a real world answer
> 
> IF, the center-line of the scope is exactly parallel to the center-line of the bore
> 
> ...


I think I understand what you are saying, but first of all wouldn't distance A and distance B be the same? Are you saying that effectively by raising A, what you are really doing is taking the the centerline of the scope from being parallel to the centerline of the bore to being angled downward toward it, which effectively creates an angle between the LOS and the bore so as to raise its trajectory to hit higher?? I think that's what you are saying, which I agree with, and thus as you increase the distance between the two lines, I.E. raise the the scope above the bore, that change in the angle has an effect on the bullet flight relative to the ground.

Personal experience yesterday. I went out to shoot my AK, which has a red dot on it. The last time I went out, I shot a really good hand loaded 123 gr sierra sp, that, believe it or not, grouped .73" at 50 yards. So yesterday I wanted to try it at 100 yards. I did not get the group I was hoping for, but the POI was 8-9" high. The red dot is 3.25" above the bore. Dead on at 50, 9" high at 100?? Has to be the height of the red dot above the bore. Sucker might be still climbing.


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## CoastalOutfitters (Aug 20, 2004)

all I'm guessing , is there may be more room for built in error


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## Chummy (Jan 3, 2006)

So if I have a scope mounted 12" high and it is zero'd at 100 yds why would the bullet path be different from a 1-1/2" high scope zero'd at 100 yds?


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## BradV (Jun 27, 2012)

Chummy said:


> So if I have a scope mounted 12" high and it is zero'd at 100 yds why would the bullet path be different from a 1-1/2" high scope zero'd at 100 yds?


The bullet path itself will be identical. The scope being high by 12" will need a large adjustment to zero at 100 yards, effectively giving you a downward line of sight through your scope much greater than the scope mounted 1.5" high. See my amazing MS paint drawing for an example. It clearly is not to scale, but it may shed some light on things about scope height.  Bullseye denotes zero point, which is identical for both rifles and the trajectory curve is identical for both rifles. The only difference is scope height. The zero being the same only changes the angle in which your crosshair is actually pointing. This in turn gives a secondary zero point further down range, when the bullet falls back below the crosshair. The higher mounted scope simply has a farther out secondary zero point.


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## Wado (May 15, 2011)

And this is why they make canted mounts so you don't run out of internal elevation adjustments for long range shooting. Excuse me, bases.


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## THE JAMMER (Aug 1, 2005)

BradV said:


> The bullet path itself will be identical. The scope being high by 12" will need a large adjustment to zero at 100 yards, effectively giving you a downward line of sight through your scope much greater than the scope mounted 1.5" high. See my amazing MS paint drawing for an example. It clearly is not to scale, but it may shed some light on things about scope height.  Bullseye denotes zero point, which is identical for both rifles and the trajectory curve is identical for both rifles. The only difference is scope height. The zero being the same only changes the angle in which your crosshair is actually pointing. This in turn gives a secondary zero point further down range, when the bullet falls back below the crosshair. The higher mounted scope simply has a farther out secondary zero point.


Bradv, great picture, and well done. A picture is worth a thousand words.


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## Bottomsup (Jul 12, 2006)

It would be more accurate if you show the line of sight as a straight line through the scope to the target and the barrel canted upward to meet the line of sight.


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## CoastalOutfitters (Aug 20, 2004)

well, 

like I said

unless you are shooting in a leap year, during a full moon cycle, in a neap tide, during a solar eclipse with well marked solar flares.





then all bets are off.................


.


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## THE JAMMER (Aug 1, 2005)

Bottomsup said:


> It would be more accurate if you show the line of sight as a straight line through the scope to the target and the barrel canted upward to meet the line of sight.


Agree.


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## BradV (Jun 27, 2012)

Bottomsup said:


> It would be more accurate if you show the line of sight as a straight line through the scope to the target and the barrel canted upward to meet the line of sight.


Personally I like to illustrate it this way because the adjustment of the scope does not affect the bullets actual trajectory. The rifle must be pointed the same way to hit the target of the same distance. If we were showing the zero point at different distances then I would agree, the rifle would be angled upwards with the scope line of sight straight. In reality it would be a combination of both, but for the ease of a drawing you would be correct.


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## txbred (May 13, 2013)

Not sure if this is the right place to bring THIS up, but mounting the scope with the cross hairs EXACTLY level with the gun is VERY important. And not having the cross hairs dead level when shooting at longer distances will cause you to miss by a few feet. The concept took me a few days to fully comprehend, but a nice illustration drove it home for me. do a google search for canting scope. actually, do a google IMAGE search for that topic:


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## THE JAMMER (Aug 1, 2005)

You are correct- totally different subject, but certainly valid. I think when you say crosshairs should be mounted level with the gun- maybe another way to say that would be to say that the scope should be mounted so that the UP/DOWN line of the scope is perfectly perpendicular to the barrel. 

The second component is that when you shoot, the gun has to be perfectly level; i.e. the reason for having a level mounted to your scope. I have this on all my long distance/accuracy guns. Put the gun up, refocus up close and see how level the gun is, adjust, refocus on the scope and fire. Cant, as you said, can be significant the farther out you go. Add that anomaly to a little bit of misjudged wind, and you are off target, even on some shorter shots.

I love ballistics. It's a subject that a lot of people don't really delve into, and wonder their whole lives why they are not shooting as well as some others. It's like the guy who shoots his shotgun, and continues have mediocre results, because he won't take 30 minutes one day to see how his shotgun actually fits. If you close your eyes, mount your gun, open your eyes, and you're looking at rib, you will shoot high almost EVERY TIME.


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