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Chair gun Pro problem

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After many thoughts I relize that my scope will probably prove to be quit close to 10x setting for mildot calibration. But I will check it. I came to this conclusion because when zeroed at 50 yds. It shoots 0.75 high at 25 yds reguardless of mildot spacing, and I also fireed 10 shots over chrony to check velocity, therefoe the only thing I can find is that the BC of the jsb 18.1 grain pellets is not 0.033 as listed in chairgun pro but must be close to 0.019 which would give results very close to mine.
Sdellinger : did you change the BC to get your results to match and if so what was listed and what did you end up using.
My concern now is are all the BC off that much, if so they appear to be worthless if this is in fact the problem.
 
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DaveF, I did not change the bc. I went with what Chairgun said. I use a 4X16 scope set on 12 power. I had to use 8.3 power in the Chairgun program to match my dot ranges. I used to have a 6X24 Tasco and 12X in the program matched my 12X dot ranges. I don't understand the math. All I know is it works. Pick a power, any power to shoot on. Zero at whatever distance you want. I use the optimum distance Chairgun gives. Then move your target to where the next dot below the cross hair hits bullseye. On my 12X Tasco it was 62 yards. When I changed scopes I shot my dot below the cross hair and it was on at 70 yards. Then I moved the target back untill the second dot hit bullseye which was 85 yards. I then shot at dirt clods untill my third dot hit a clod which was 98 yards. I manipulated Chairgun untill I matched my trajectory. Just show a cross hair of your scope in the Chairgun program and change the power up or down and eventually it should match what you are shooting. Worked for me as I posted a video hitting a pigeon at 132 yards using the 6th dot below my cross hair. Have fun, Scott
 
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DaveF,

Getting the different components to "align" can be a bit tricky - but when it happens - you'll love it. I have a Bobcat MK2 (.25) and the ChairGun app is spot on with real world results.

Some thoughts for you... time to check a number of things.

Are you shooting level (or canting errors)? Is your scope reticle level?

Is your Bobcat power setting on HIGH?

Re-chrony your gun lately?

Accept the BC value for your pellet via the Chairgun app - trust me - it will likely be close enough. Just make sure that the other performance and environmental data points are correct.

Measure target distances with a tape measure or an accurate range finder - verify! If your scope distance indicator is way off - you might have to re-calibrate that by loosening set screw - adjust to proper measured distance then re-tighten. BTW - scope distance indicators sometimes make for lousy distance measuring tools - its primarily there to reduce parallax.

If you have been making numerous turret adjustments, recenter your scope erector tube (use the rotate on box grooves method as that is the best method (see youtube) - Hawke recommends NO other method). Scopes that have been adjusted beyond their optimum optical/mechanical range are a HUGE contributor to "accuracy" issues. The guys at Hawke Optics take calls all day long from customers with "broken" scopes (read: user error). :)

One other important note - when first zeroing your scope - adjustable mounts should do the heavy lifting in terms of bringing the POI close to bullseye. It's a bad sign to shoot once and then crank the turrets over and over... that leads to many scope accuracy/parallax issues). Turrets are for very fine adjustments/small distances.

Did you adjust your front scope ocular eyepiece for your specific vision? Remember - you are adjusting that so the RETICLE is clear - not the distant image. And, if you did change the front ocular to accommodate your vision you have now changed the length of the scope - which, you guessed it, now changes your scope magnification from the factory design. To "re-calibrate" - you need to set scope to 10x (which is true mil-dot for the Eclipse) and set a ruler out - adjust magnification so that ONE mil-dot distance =3.6 inches at 100 yards (or 1.8 inches at 50 yards, or .9 inches at 25 yards, etc.) Once re-calibrated - mark your new power indicator position on the scope so that its accurate through the magnification ranges.

Finally, after entering your numbers into ChariGun - when I select 795 fps, I show POI at 25 yards to be .75 inches high (as per your experience) and .82 mil-dot (10X) and 1.63 mil-dot at 20x. Re-chrony and check power settings.

Good luck and keep us all posted
 
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GIGO

All the Chairgun Pro "errors" I had was because of data errors I entered. Now that is a strong statement, so please give me the opportunity to explain -

At first I used the default BC, the ballistics curve is quite sensitive to the BC, the sure way is to measure it.

Scope dials, in my experience aren't very well accurate or calibrated. I'm not too worried about this for the parallax but the magnification is important in this context.

The magnification of my scope had been unknowingly changed, looking through the scope it wasn't obviously, but the holdovers indicated a problem. So I now have a bit of tape on the adjustment ring so it cannot move off my chosen magnification. I've also seen people changing magnification in the field, but use the same holdovers (shouldn't be a problem with FFP scopes).

It was by entering slightly different values in Chairgun Pro, one at a time, that I got an understanding of the sensitivity of each factor. Each time I took the care to make sure the parameter in Chairgun Pro was the same as gun the real world experience and Chairgun Pro converged.
 
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Not sure I'd go as far as 'stupid', awkward to work with maybe, or even natural.

'Natural?, Well it does come from a time when we related everything to the things around us we could see - an inch being the end of the thumb to the first joint, or the yard being from finger tip to nose when the arms is held horizontally to the side, or horse power... well that's pretty obviously. 

It it could be argued that the real ease of the SI unit (metric) is that it uses base 10 to count. After all, what is obvious about a metre being the distance light travels in a vacuum in a fraction (1/299792458 th) of a second? I can pace something out, or use my thumb ("rule of thumb") whereas I cannot 'see' or touch a metre.
 
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Cricket
Well Yesterday I went into autcad and made a drawing with 5 accurate circles in it of 1, 2, 3 , 4 & 5 cm in diameter.
Followed that up by going to the range and setting this target out at exactly 50 meters. With the hawke eclipse scope set on 10x the 5 cm circle split as exactly as I could see 2 adjacent mildots. It was so good I did not even bother using the other circles at there respective distance, however in hindsite I should have tried a couple.
I then shot a minimum of 1 5 shot group at 10, 15, 20, 25, 30, 35, 40, 45, 50, 55 & 60 yds with zero hold.
The wind was gusting so it took quit a while waiting for calmer periods but even so the groups were not great so I shot multiple groups at 50, 55 & 60 yds and averaged the results. I then measured the rise and drop at the various yardages and compared them to the results from chairgun pro using bc from chairgun table and all other data input without manipulation. Most of the rises and drops from a zero hold were within 0.1 inches of those listed in chairgun pro, however 35 yds was 0.2 less rise, 40 yds was 0.4 inch less rise, but 45 yds was only 0.1 inch less rise.
In addition 55 yds was nearly 0.5 more drop than chairgun prediction, and 60 yds group was 0.1 inch more drop. All of these are with a 50 yd zero.
Under good calm conditions this gun can shot sub 1/2 inch 50 yds groups, however on this day the 3 60 yd groups ranged fron 1 inch ti 1.3 inches and 3 50 yd groups from 3/4 to 1.1 inches with 55 yd groups in between these.
I Do not have much experience with wind effects on these light pellets but I guess that possibly these Vertical differences are a result of the wind just as the horizontal spread is. My observed groups were basically spread horizontally for the most part.
All of this leads me back to my original problem as to why I had on several occasions 0.75 rise at 25 yds shot at home in calm conditions when chairgun said it should be 0.4 inches.
Most interesting yesterday the 25 yd groups only resulted in an average of 0.34 inches.
Now after all this though and effort I can not explain it.
Any ideas would be welcome.




 
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Cricket
Are you saying that you have to use a differebt bc for every distance ?
Thanks for your offer, I may take you up on it.


x-hairs
I did a new complete chrony string 2 days ago and got and average velocity of 872 fps with 18 gr jjsb as compaired to the 888 fps I was using which was before AOA replaced the barrell and tuned it.
When I got it back I fired 10 shots over chrony and it did not seem different so I stuck with 888fps but now its 872.

Failed to mention one big thing from my testing on the 27th. The poi at 25 yd with 50 yd zero and same 18 gr jsb is now 0.34 inches high and chairgun is 0.40, very close but why is the poi changing from the 0.75 I got on several occations at the house. This would have nothing to do with magnification because I was holding on.
Can the breeze be pushing the pellet up and down ? Even though it I tried to wait it out and was not more than 5 to 7 mph by my estimation.
Or are the cross hairs in the scope moving?
Maybe with change in focus?
 
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