Scope height?

W

William Suter

Well-known member
I had my rifle sighted in at 100yds. Today I raised it a half inch for better eye sight alignment. Is it going to be high or low at 100yds?

(I'm guessing low, just not sure how much.)
 
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William Suter said:
I had my rifle sighted in at 100yds. Today I raised it a half inch for better eye sight alignment. Is it going to be high or low at 100yds?

(I'm guessing low, just not sure how much.)
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it's all a guess till you shoot it. not sure why that would even be a question till you squeeze the trigger. could be high, low, left or right...and will likely be a combination
 
c_bass16 said:
it's all a guess till you shoot it. not sure why that would even be a question till you squeeze the trigger. could be high, low, left or right...and will likely be a combination
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LOL, I really don't think it will be a guess, bullet impact will go one way or the other. I'm trying to imagine the rifle locked down in a vise and zeroed. Then raise the scope with a 1/2" spacer. (No dials have been adjusted) Now reposition the rifle so the crosshair is back on the bull, (still not adjusting the dials), where will the bullet impact, high or low?? Keep in mind that no adjustments have been made.
 
" Now reposition the rifle so the crosshair is back on the bull" irrelevant - like aiming the rifle down. It will be high until you re-zero. How much? depends on the quality of the sims, etc.
 
William Suter said:
LOL, I really don't think it will be a guess, bullet impact will go one way or the other. I'm trying to imagine the rifle locked down in a vise and zeroed. Then raise the scope with a 1/2" spacer. (No dials have been adjusted) Now reposition the rifle so the crosshair is back on the bull, (still not adjusting the dials), where will the bullet impact, high or low?? Keep in mind that no adjustments have been made.
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Youre gonna unhook your optic and remount it with a spacer...your zero isn't going to remain true so your hypothetical shift isn't going to be consistent or repeatable anyway.
Redo it 5 times, it'll likely be different every time.
 
In a perfect world it would be low, however, that would be assuming both risers measure and seat perfectly. You are raising your POA from original setting, so when you aim at the target you would be lowering the muzzle of the rifle. ETA: The crosshairs are same as front sight on a rifle. Move the front sight in opposite direction you want to move POI. When adjusting rear sight, the opposite is true, move rear sight in direction you wish to move POI.
 
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hm, that's kinda what I'm getting at. I know until I shoot it I won't know, but hypothetically, in a perfect world, it should be low. This ain't the movies and I know when you take a scope off then put it back on, its gonna be different. Maybe not by much but it will be off. I had my new AR zeroed at 100yds but felt like I was looking over the scope. My friend looked through it and couldn't see through it at all. I added the riser today and fixed the issue and was just curious which way bullet impact will go. Dang now I even have myself confused. Only one way to find out for sure. To be continued..........
 
That throws off all of your holds so better get out the ballistics calc. I don't know what gun, bullet, speed, or zero the rifle currently has so its just a guess.
 
First, I haven't even worked up a load yet so ballistics and hold overs don't really matter yet. Let me explain once more what I'm thinking. Once again we're in a perfect world and I have my rifle in a vice. Scope is dead on the bull and so is bullet impact. I raise the scope 1/2" and reinstall. Now the barrel/POI is still on the bulls eye but the crosshairs (I think) should be higher than the bull. Then if I loosen the vice and adjust the rifle so the crosshairs are now back on the bullseye, the barrel is now lower than the bullseye. So POI should impact the target lower. Does this make any sense? Does to me but I'm not the sharpest knife in the drawer.

Or am I just total wrong???
 
My guess is/was it'll be 1/2" high.

So I went to JBM, put in a scope height of 1.5", 100 zero makes it 2.6" low at 200.

I changed scope height to 2.0" with a 100 zero, it was 2.1" low.
 
William Suter said:
Only one way to find out for sure. To be continued..........
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Guess it depends on whether the cross hairs represent your front or rear sight:unsure:. I believe cross hair is same as front sight. We shall see. :)
BBK said:
That throws off all of your holds so better get out the ballistics calc. I don't know what gun, bullet, speed, or zero the rifle currently has so its just a guess.
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Absolutely. These new sight bases and scope bases are much more precise than they were years ago. Many of my scopes and all of my target rifle sights can be removed and replaced without changning POI.
alf said:
My guess is/was it'll be 1/2" high.

So I went to JBM, put in a scope height of 1.5", 100 zero makes it 2.6" low at 200.

I changed scope height to 2.0" with a 100 zero, it was 2.1" low.
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Looking forward to range report. I do know that if you shim the front scope base it lowers the bullet impact and vice versa.
 
If its picatinny and you put it back in the same slots then it shouldnt change the POI other than it will be shooting lower now. (Scope is higher, so you have to point the gun down towards earth to bring crosshairs back down to target, making poi low). If its dovetail, youll never get it back in the same exact spot so taking a scope off and putting it back will always change POI.
 
BBK said:
If its picatinny and you put it back in the same slots then it shouldnt change the POI other than it will be shooting lower now. (Scope is higher, so you have to point the gun down towards earth to bring crosshairs back down to target, making poi low). If its dovetail, youll never get it back in the same exact spot so taking a scope off and putting it back will always change POI.
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This is my original thoughts as well. You have to lower the rifle to put the crosshair back on the bullseye and that lowers the barrel. Seems to me that would make for a low impact.
 
Forget the part about tilting the rifle. Mounting the scope with nothing but increasing height, scope line-of-sight will be higher. POI will be lower. Theoretically.
 
The angle that barrel needs to compensate for gravity (bullet drop as it travels outside the barrel) doesn't change. You will need to recalibrate the scope(to the path of the bullet). As the line of sight in relation to the path of the bullet is/was changed when the scope is raised further above the center of the bore.
 
Theoretically - low. You've raised your line of sight 1/2". But it would be shi* house luck if that actually worked. Anytime you pull off your scope and re-torque it back down you should check it on paper.
 
tawnoper said:
Theoretically - low. You've raised your line of sight 1/2". But it would be shi* house luck if that actually worked. Anytime you pull off your scope and re-torque it back down you should check it on paper.
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This is true. Its all theory. In theory it shouldn't change zero because pic rail locks in the same every time. In theory it should only be off a tiny bit low due to height adjustment. Its all theory. What we know is youll be on paper at 100yd and you can adjust from there in two shots.
 
Yep…Theoretically Low, assuming you raised the optic perfectly parallel to its original position by 1/2” and didn’t make any turret adjustments.

How Low will it impact at a given distance would need to be determined at the range.
 


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