Chair gun Pro problem

[DaveF]

I have been using chair gun Pro to determine velocity curve for my FX Bobcat in 22 cal. I have been shooting JSB 18.1 great pellets which chronological at average of 888 fps, with a ex of 22 fps and 40 shots filling to 2800 psi
and shooting down to 2100 psi.Most of my shooting is at range. Sited in at 50 yds.
My problem is that chair gun says poi at 25 yds should be plus .4 mill dots however in reality the poi is about plus 1.5 mill dots at 25 yds. This is with a Hawk Eclipse 6 x24 scope with 10th mill dot reticle.
I am using scope at 20th so I should use 0.8 mill dot hold, but group indicates 1.5.
I am using a b c of 0.033 right from chairgun.Don't know what's wrong. B C would have to about 0.022 to get these numbers

 

[Alan]

I've heard of this issue before on GTA. And, if my memory is correct, it was a error in the BC, however, I can't say what the numbers were or should be. 

 

[SDellinger]

I find I have to manipulate Chairgun to fit what my FX 500 does. You can't change what your gun does so change Chairgun to show what your gun is shooting. I shoot 25.4 JSB pellets At 890fps. I use a Nikko Sterling 4X16 Nighteater scope on 12X. To get Chairgun to agree with my trajectory I had to input 8.3X in the program. When I used a Tasco 6X24 12X in the program worked fine. Now 8.3X works. Interesting 12 Is half of 24 and 8.3 Is about half of 16. Whatever. I shot a pigeon at 130 yes and I used the dot Chairgun said to use. Have fun, Scott

 

[DaveF]

So you change magnification to match field data.
have tested this out on paper shoot at different distances
My scope is suppose to be correct at 10x 
sounds like you may be shooting yours at power other than its true mil calibration.
one of Teds videos on mill dot shooting stated if cal is 10x just double mil dots at 20x
Guess you are saying chairgun data is wrong if you apply it correctly,
Is always true?

 

[DaveF]

So you change magnification to match field data.
have tested this out on paper shoot at different distances
My scope is suppose to be correct at 10x 
sounds like you may be shooting yours at power other than its true mil calibration.
one of Teds videos on mill dot shooting stated if cal is 10x just double mil dots at 20x
Guess you are saying chairgun data is wrong if you apply it correctly,
Is always true?

 

[DaveF]

Just tried to change power setting in chairgun by setting it in the retical page.
could not change it higher than 24x which is my scope and this was no where enough 

 

[DaveF]

I tried changing just about every setting in chairgun and I can not make it equal my field results.I went on Ted holdover and looked at his mill dot video. The gun he was using to demonstrate how to use chairgun pro was very similar to mine only a little faster.
His mil dot holds were also very similar to what I get from chairgun for my gun.

So now I am wondering about Mt mill dot spacing in my scope. It's a Hawke Eclipse 6x24. Box says 10th mill dot, Can't figure out why I have to use 4 times the chairgun mill hold on 10th and twice that hold on 20x.
Any help would be appreciated

 

[fe7565]

Are you sure you set zero range to 50yards? Did you make sure the scope height in Chairgun is set right? Also, did you match your scope's 1/8" or 1/4" 'Clicks/MOA' in Chairgun? You can manually change the scope magnification all the way to the left of the screen in Chairgun.

 

[DaveF]

I do have the far zero set to 50 yds, as well as the correct scope height and 1/4 inch clicks.
With my Bobcat Sited in at 50 yds with 18 grain JSB it is 3/4 inch high at 25 yds. Scope is 2.75 above bore.
That 3/4 inch looks like .75 mil dots with scope on 10 x and 1,5 mil dots with scope on 20 x.
Chairgun says 0.4 at 10 x and 0.8 at 20 x which is exactly half of what I see in scope

 

[mapuia]

I have the same problem with chairgun. With my air arms s510 and hawke sidewinder 30 3-12 at 860fps with jsb 18. Chairgun indicates about 6.8 mil dot holdover which actually is 5.3 mil. So did some research about bc variation and chairgun itself has various bc to select with my 18's depending on altitude temp etc. So i change the bc from .033 to .045 and spot on

 

[SDellinger]

This is the range card I made from chairgun. I zeroed my gun with the yardage Chairgun recomended then moved my target untill I hit the bullseye at the first dot below the cross hair and recorded the yardage. I did this for all the dots below the cross hair and recorded the yardage for each dot. I shoot on 12X and don't change. If you have a first focal plane scope you can shoot at any power. I worked with Chairgun untill it matched my yardage and printed this card. Works for me. Have fun, Scott

 

[fe7565]

"mapuia"I have the same problem with chairgun. With my air arms s510 and hawke sidewinder 30 3-12 at 860fps with jsb 18. Chairgun indicates about 6.8 mil dot holdover which actually is 5.3 mil. So did some research about bc variation and chairgun itself has various bc to select with my 18's depending on altitude temp etc. So i change the bc from .033 to .045 and spot on

As far as real life BC: there was a thread (cannot find it now) on this forum where Yrrah tested a new batch of .25 JSBs vs old batch and the BCs differences were similar like .033 and .045 . That's with a .25, but wonder if this may be true for .22 JSBs too.

 

[Longbrownbox]

Well said Scott! What's really important is being able to hit the target when you want. I've already seen your video shooting a pigeon at 130 yds. It works and that's important. 

 

[DaveF]

Thanks to all for your comments. I am going to try your idea Cricket. I am thinking that the mil dots on my scope are actually 1/2 mill dots and not 1 mill dot even though they are not suppose to be. I dont know how this could be,I will let you know

 

[SDellinger]

Do many people range with mil dots? Especially ranging a small bird. Rangefinders are so cheap now. I don't care if my mil dots aren't true mills or moa or what ever or what power I'm on. I just want to know I'll hit where the dot indicates. Hope this makes sense. I'm not saying anything bad about using mil dots but it seems to me people get too wrapped up in the process sometimes. Have fun, Scott

 

[DaveF]

I thought the program took care of that when you put in the altitude, temp. and barometric presure.

 

[DaveF]

"SDellinger"Do many people range with mil dots? Especially ranging a small bird. Rangefinders are so cheap now. I don't care if my mil dots aren't true mills or moa or what ever or what power I'm on. I just want to know I'll hit where the dot indicates. Hope this makes sense. I'm not saying anything bad about using mil dots but it seems to me people get too wrapped up in the process sometimes. Have fun, Scott

well if you don't know what you mil dots represent you can't use them for holdover

 

[DaveF]

Just one more coment I have is that my Hawk Eclipse side wheel does not indicate anywhere near the correct distance when in focus, eg. at 25 yds it's more like 30 and 50 is more like 60 or so. Don't know if individual eye sight comes into play here or not. I have noticed this on several scopes in $300 to $500 price range.

 

[SDellinger]

I shoot at zero which is 52yds for my gun. I use the dots for aiming but I don't know if they are true mil dots or not. I just know where each dot hits. I don't have half marks on the reticle and I just estimate the distance between dots. At closer than 52yds I use the dot above the cross hair. I shoot at 12X all the time. I've shot enough that I pretty much know where to aim. Don't get me wrong, I miss some times but with the FX 500 if I hold correctly it's always my fault. Happy Thanksgiving to all, Scott

 

[SRGTO04]

Here is a link to Youtube on how to calculate your own BC for any gun. I hope this helps