Scope adjustments are more than an MOA Now what?

[seanhagerty]

I was doing a tracking test on a new scope, Bushnell Tactical elite 6-24X 50mm. The turrets are supposed to be 0.25 moa clicks.

http://www.fotolode.com/images/sabersix315/imag0141.jpg

I shot this today. The shots that tell the story are the 18 MOA adjustment being 20 inches high and the 36 MOA adjustment being 40 inches high.

I shot data out to 600 yards today, so I have that for a comp next weekend, but am unsure how to calculate other range data. Any thoughts?

[JackinSD]

In both cases you are getting 6.41% more adjustment than you should be. If you are using a ballistic program it may have an adjustment that can be made. I know that Applied Ballistics has one.

[seanhagerty]

That is the answer. I found it an adjustment for Applied Ballistics and for Shooter.

[thomae]

This is really a simple "math in real life" problem.
Under ideal conditions, one MOA subtends 1.047 inches at 100 yards.
Your scope's "MOA" subtends 1.111" at your 100 yards. The difference is .064" or 6.4%
SO we do the math and come up with the following table:


Your Scope's MOA adjustment
Actual point of impact (POI)shift (inches) at 100 yards
Ideal MOA adjustment
Ideal POI shift (inches) at 100 yards


1
1.111
1
1.047


2
2.222
2
2.094


3
3.333
3
3.141


4
4.444
4
4.188


5
5.555
5
5.235


6
6.666
6
6.282


7
7.777
7
7.329


8
8.888
8
8.376


9
9.999
9
9.423


10
11.111
10
10.470


11
12.222
11
11.517


12
13.333
12
12.564


13
14.444
13
13.611


14
15.555
14
14.658


15
16.666
15
15.705


16
17.777
16
16.752


17
18.888
17
17.799













MOA is MOA regardless of the range. For your scope, to approximate a "real" MOA, you need to subtract a extra MOA for each 17 MOA you wish to move your POI, (subtract one click for each 17 clicks).

Reading the chart above: If you wish to move your 100 yard POI 17 MOA (17.799") click up or down 16 MOA on your scope which will move your POI 17.777". The difference between what you want and what you dial in will be .022 inches. I doubt that even you will be able to shoot so precisely that you will be able to tell the difference.

Possible error source (rhetorical questions, you don't actually need to answer) :
How precise is your 100 yard range measurement? Could there be any error there?
How did you actually measure your scope's change in elevation? Any chance of error there? It might be very different when you are shooting.

Most scope"MOAs" are approximate, and if the error (between "scope" MOA and "real" MOA) is linear and constant as yours seems to be, one can easily determine precisely how far X number of clicks will change your point of impact.

Bottom line: Don't worry so much about how far each click moves your POI until you actually have your sight dope and have figured out how many clicks up you need at any particular distance. Then, when you are adjusting just a few clicks in either direction to compensate for the light or the wind, it won't matter so much as the real life error will be smaller.

I hope this clarifies and does not muddy the waters.

[JackinSD]

That is the answer. I found it an adjustment for Applied Ballistics and for Shooter.

Glad you got it!

[seanhagerty]

WOW!

Thanks for all the info. I had already arrived at the 1.111111" figure and had input it into both of my ballistics calcs. The 100 yard distance was arrived at with a laser range finder. It is also the 100 yard line for our comps. So I am confident in that.

The change in elevation- The adjustment was pretty evident. The numbers were staring me in the face. The holes in the target above tell the story. I measured them with a tape measure.

SInce I have the ballistics apps adjusted my problem is solved. Thanks for your help.

Sean