Ballistic calculator

[royinidaho]

I'm using this thread to sharpen my skills with exbal. Hope you don't mind.

The information provided says that you are zeroed at 272 yds. (2.5" high at 100)

Come ups @ 500 = 5.25

You gave the info for 500. I could find no 750 data Drops)

1.9" LOS above LOB seems a bit high. How was this measured?

You don't need to shoot all of the distances (too time consuming and expensive).

Verify your 2.5" @ 100. Then get good 'actual' drops at say 500, 600 and 750.

These distances should be sufficient to be able to connect the dots.

Post your results and we'll go from there, OK?
Also, is there a local airport where you can get barometric pressure @ altitude, not corrected to sea level?

[eric2381]

CANOE -- CNEWS: Weather

I found the current barrometric pressure here.


I measured the sight height with my caliper. I'll measure again, to be sure.


I am bang on 2.5" high at 100 yds. I need to go up 6 MOA to be bang on at 500 yds. I need to go up 1.75 MOA to be right on at 350yds.

[eric2381]

I stand corrected. My sight height it 1.7", not 1.9".

[eric2381]

That still doesn't bring me around to the numbers that I actually shot.


I'm gonna have to go out shooting again to get some more numbers.

[royinidaho]

Originally Posted by eric2381

I stand corrected. My sight height it 1.7", not 1.9".

That'll make a difference!

Formula for determining LOH over LOB.

Distance from top of end bell to bottom of barrel minus ((1/2 of scope end bell diameter) plus (1/2 of barrel diameter at front of scope end bell)) All measured at the same point.

If there is a sloped base then some fudging be necessary.

With the new LOS value and the old atmos data here's what I what I came up with.

As close as I could get thing to jive with your drops are:

100 yds = 2.585" high
350 yds - 1.985 MOA (0.235 MOA or 0.8225")
500 yds - 5.961 MOA (0.039 MOA or 0.195")

Inputs were:
MV = 2965 FPS
Line of Sight above Line of Bore = 1.70"
BC = 0.48

[eric2381]

Is it common to find that the advertised BC to not be tue???

[liltank]

Originally Posted by eric2381

Is it common to find that the advertised BC to not be tue???

Yes!!! I'm having the same problem that you are having. I am currently trying to find out my range card. I need 13 MOA at 680 and 29.2 at 1070yrds. The problem I am having is getting those to numbers to appear at yardage. If anybody would care to crunch, by all means give it a go. 54deg. 1000ft elev. 60%humidity, 29.94 baro, 2930fps, 200grn SMK.

I've tried adjusting bc. and can get it to match the 680, but not the 1070. It does not give me the proper come up at the longer distance. I wish they had a scratching your head emoticon.

Tank