# Exbal- sight ht.

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by soren, Jun 18, 2008.

1. ### sorenWell-Known Member

Messages:
258
Joined:
Mar 9, 2008
On the Exbal program it asks for the scope height above the bore of the rifle. I didn't notice anything about using a straight base or an incline base. Do you still just plug in your basic sight-in numbers and go from there? I guess the angle of the base doesn't really matter...it comes down to the angle of the bore in regard to the postion of the retical.

2. ### royinidahoWriters Guild

Messages:
8,853
Joined:
Jan 20, 2004
Soren,

Tho I don't use Exbal yet, I've read that the sight height matters.

With slanted bases its a bit difficult bout doable.

Determine the diameter of the end bell.
Determine the diameter of the barrel
Determine the distance from the top of the end bell to the bottom of the barrel.

Then: Distance from bottom of barrel to top of bell - (1/2 End Bell dia. + 1/2 barrel diameter) will give a good start.

Then shoot drops and adjust BC etc to get close. Then, as was said by someone on here, fudge the sight height to get spot on.

Hope this helps...

3. ### jwp475Well-Known Member

Messages:
2,595
Joined:
Feb 4, 2005
I measure my scope hieght from the center (length wise) of the scope and this has worked perfectly for me so far.

4. ### sorenWell-Known Member

Messages:
258
Joined:
Mar 9, 2008
I was really wondering if having a cant on the scope(ex. using a 20moa base) really changes how the program works. I know that the center of the lens to the center of bore is a fixed measurement. But if you had two rifles same cal. and such, same bore/sight ht, and both zeroed at 100 yards; but one uses a 20 moa base and the other has a level base. Will equal come-ups cause the same results regarding shot placement.

5. ### royinidahoWriters Guild

Messages:
8,853
Joined:
Jan 20, 2004
I'll go to the far edge of my thinking on this one.

All things being equal, exactly equal, except for the cant of the base, after 100 yd zero is precisely set, the zero settings on the elevation turret will differ. However, the number of clicks for a given yardage other than the 100 yd zero will be exactly the same.

I've never tho't that far ahead, thus any corrections would be appreciated.

Me thinks it "has" to be that way or MOA per click would vary with the scope cant.

6. ### MagManWell-Known Member

Messages:
1,008
Joined:
Dec 20, 2002
Not to stomp on this thread but Roy you said you don't use Exbal yet. Is this because you don't have a Palm & software?

Do you have a serial port on the back of your computer? The exact opposite of the one your monitor uses.

7. ### royinidahoWriters Guild

Messages:
8,853
Joined:
Jan 20, 2004
MagMan,

I have nothing but sorry excuses. I have a PC server, A Mac Mini a supper hootie lap top and a pocket pc with tons of software on the pocket pc. Mapping, GPS, GIS etc.

As soon as I get to where I need Exbal or some such, which should be later this summer I'll snap up on it. So far my spread sheets on the pocket pc do just fine if I remember to punch in the atmospheric conditions. That is to say that it works well at "the range" but will need Exbal when I hit the hunting slopes.

Oh yea, I use RSI on the laptop. Really good but no version for pocket PC.

Now back to the scope height topic.......

8. ### milanukWell-Known Member

Messages:
806
Joined:
Jan 21, 2002
If you want to be particular... take a set of calipers then: measure the scope tube diameter, measure the receiver diameter, measure from top of tube to bottom of receiver, subtract 1/2 tube diameter and 1/2 receiver diameter = centerline of scope above centerline of bore. Then you have people who get all twitterpated over the difference in height between the fore and aft ends of the tube when using a 20 moa canted base, and try averaging the two measurements...

Close enough: Take a ruler, and eyeball it from the middle of the scope tube to the middle of the receiver (hint: the gas port on the side of the receiver just above the stock is a good reference), and get it w/i 1/4".

If you are bored, plug in different numbers (1.5, 2, 2.5) and see how much it matters (not much). 'Close enough' works pretty darned well.

YMMV,

Monte

9. ### jmdenWell-Known Member

Messages:
2,725
Joined:
Nov 2, 2003

I've got Exbal and the same question as the original poster. Got a 0 moa base at the moment and am thinking of asking Seekins to make me a 10 moa base. But am not quite sure what the cant does to the program, if anything. If I recall correctly from similar past discussions, the cant doesn't matter, but I'd sure appreciate a refresher on this...

10. ### edgeWell-Known Member

Messages:
1,088
Joined:
Nov 4, 2005
Thinking out load, I think that it should be the height of your eye ,as you look through the scope, above the centerline of the barrel.
IMO, you normally use scope height because the scope is at 0 degrees, and so is your eye.

Perhaps not

edge.

11. ### EagletWell-Known Member

Messages:
2,779
Joined:
Feb 2, 2005
light bulb +1