Scope height?

alf said:
For the "it's gonna be low" guys, explain the JBM results.
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You probably went into JBM and left the sight in yardage the same but only changed the line of sight from 1.5 to 2". That's not what the OP asked. You'd need to make scope adjustments to achieve the way you used the ballistic calculator. He asked if he ONLY added a 1/2 spacer where would it hit.
 
tawnoper said:
You probably went into JBM and left the sight in yardage the same but only changed the line of sight from 1.5 to 2". That's not what the OP asked. You'd need to make scope adjustments to achieve the way you used the ballistic calculator. He asked if he ONLY added a 1/2 spacer where would it hit.
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I only changed the scope height 1/2" with a 100 yard zero for both, there was a half inch higher change on POI at 200.
 
tawnoper said:
You probably went into JBM and left the sight in yardage the same but only changed the line of sight from 1.5 to 2". That's not what the OP asked. You'd need to make scope adjustments to achieve the way you used the ballistic calculator. He asked if he ONLY added a 1/2 spacer where would it hit.
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He already had a 100 yard zero, when you raise the scope a half inch, all things being equal, POA & POI will be a half inch higher.
 
2" - - - - - - - - - - - - - - - - -+
1"_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _+
Bore--------------------------- 0

If you move scope up an inch, + is another inch above bore. If you now point the scope (+) at the bullseye (0) at 100 yards, where is the bore going to be pointed now?
 
tawnoper said:
As I said. Doesn't work like that.
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Indeed. No online calc can do this without the end user doing a bunch of math to input the correct zero yardage. 100yd zero at 1.5 then 100yd zero at 2" inputed will move the POI up 1/2" but thats not what he is doing in the real world
 
spotstalkshoot said:
For me I would HOPE its still on a sheet of paper at 100 yards, than I wouldn't have to go pull the target and move it in to 25 yards and start all over. Shots will definitely needed.
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If any changes being done in the course of raising the scope caused it to be off paper at 100yd, the scope is broken. At most it will be an inch off id guess, due to different torque or tolerances in the riser plus the actual increase in height.

I can switch scopes between rifles and rarely ever see them more than 2-3" off.
 
Just for fun.

Let say you have your rifle on sandbags and place a target right up against your muzzle. Lets say, just for fun, you can see the target bullseye clearly in your scope. Line up the bullseye in the crosshairs and take a shot. If your rings are 1.50" your line of sight will be 1.5" above the muzzle and the bullet hole is going to be approx 1.5" low.

Now, leaving your rifle on the sandbags, remove scope and add 1/2 spacer to base lifting it to 2" .Your line of sight will be 2" above the muzzle. Line up bullseye in crosshairs and take a shot. The bullet hole will be approx 2" low.
 
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When you start adding spacers your adding mounting and machining differences to the point that I wouldn't take it into the field until it's been to the range to verify zero.
 
As we all know bullet path is an arc rather than straight line, but simpler to diagram as straight line.
Top line represents line of sight through scope as it had when set for 100 yd POA/POI after moving scope to 2" rings.
Middle line is line of sight through scope mounted 1" above bore.
Bottom line represents straight line through bore to 100 yard target.
1740784327785.jpeg

X on top line is representation of where the cross hairs should be (again, in perfect world ) after the move. Now, move the rifle so that cross hairs are centered on the target and see where bullet (should) land.

Then take it to the range and find out how far you are off. ;) :LOL:
 
OK, got off my tunnel vision & un-inserted my head......;)

Raising the scope mount will lower your muzzle with the same POA, duh....

Wouldn't it be just the 1/2" POI difference at 100 yards?
 
alf said:
OK, got off my tunnel vision & un-inserted my head......;)

Raising the scope mount will lower your muzzle with the same POA, duh....

Wouldn't it be just the 1/2" POI difference at 100 yards?
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Depends on bullet travel at that range, but yeah probably. Not taking into account any other possible changes in mount position
 
Great post!! Lots of opinions. I have to go to a funeral Saturday for my old hunting buddy but will do my best to get out Sunday just to see what difference it really made.
 


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