Stupid 600yd scope adjustment question.

[ironworkerwill]

I've got the calculations from Jbm ballistic calculator with a 300yd zero I am 66.1 inches low at 600yds. Wouldn't an 11inch elevation increase put me nearly dead on at 600yds?

It has -10.6 MOA in the drop column by the 600yd line according to the calculator. So really it would be 10inches and a "click" for 1/8'' increments.? Or am I way off base?

 

[dmurdach]

I am fairly new to longer range shooting and someone smarter than I may come along and correct me if I am wrong. A 66 inch drop at 600yds would be an 11 inch correction at 100yds. So approximately 11 MOA or about 88 clicks on your 1/8 MOA per click scope. each 8 clicks would be 1MOA or 1 inch at 100 yds or 6 inches at 600 yds (all numbers are approximate for easy calculation as 1 MOA is actually a 1.047 inch I believe)

 

[ironworkerwill]

Thanks, I was having crainal/anal inversion.

 

[v8stang289]

I use the following formula:
(inches of drop)x(100/(target distance in yards))x(1/(value of 1-click in inches))

In your example,
(66.1 inches)x(100/(600 yards))x(1/(1/8))=88.13 clicks

Since we are interchanging inches and MOA in click values, there is a little error, but it is fairly small. You can adjust for it by dividing the formula by 1.047 for 84.17 clicks.

I mapped my ballistics charts out in excel, and used that formula in a chart to give me the number of clicks at a given distance at a glance. It works well for me.

 

[strambo]

A 66" elevation increase will put you on at 600yds. Or an 11 MOA increase. But not an 11" increase...

Start thinking in MOA not inches. You need to come up 10.6 MOA, multiple that by your click value per MOA and there you are. 10.6*8=84.8 (85) clicks. (The difference in how I did the math in a simpler version vs. how V8Stang did it is only a theoretical 2.25" at 600yds. Ranging, atmospheric, and wind errors will eclipse whether 85 or 88 1/8 MOA clicks is better.)

This is why scopes with Mil reticles and 1/10 mil clicks are popular, the math is super easy. Come up 3 mils, that equals 30 clicks. 6.5 mils, 65 clicks etc.

 

[ironworkerwill]

This is why scopes with Mil reticles and 1/10 mil clicks are popular, the math is super easy. Come up 3 mils, that equals 30 clicks. 6.5 mils, 65 clicks etc.

Yep, the calculators have out put data for both Mil and Moa. I've been told by several folks that Mils are much easier to figure.

I've decided that my next scope will be in mills, when funds will allow. The "red dot" on my AR died Saturday so the AR can wear the scope I have on this rifle.

is only a theoretical 2.25" at 600yds.

Ok, so if I were to adjust the turret UP 2 1/4'' that would be the correction for the 600yd zero? Sorry for the ignorance.


Thanks for the math guys!

 

[strambo]

Ok, so if I were to adjust the turret UP 2 1/4'' that would be the correction for the 600yd zero? Sorry for the ignorance.


Thanks for the math guys!

Not sure what you are getting at? I was pointing out that the formula I used of 10.6 MOA * 8 was within 2 1/4" of the longer more complicated one. Neither will be perfect as there are many variables.

You need to verify your actual come ups by shooting at distance and adjust your ballistics chart accordingly to match the real-world data.

Be careful with the charts, garbage in/garbage out. It is pretty easy to mess up an input.

 

[Driftertank]

1 MOA = 1.05 inches at 100 yards.

At shorter ranges, the difference is negligible. But you start reaching out past 500 yards and it matters.

Example: ranged a target using my MOA Reticle once, using 1" per 100yd ballpark figure, it came up as 900yds. Throw in that extra 5% variable, you realize it's actually closer to 950. With the trajectories of a .308 at that range, it's the difference between a good hit and a clean miss.

 

[ironworkerwill]

Not sure what you are getting at? I was pointing out that the formula I used of 10.6 MOA * 8 was within 2 1/4" of the longer more complicated one. Neither will be perfect as there are many variables.

Ok, I understand you now. I have a cough syrup influenced mental fog.