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 Post subject: Mil dot question
PostPosted: Sat Dec 15, 2012 8:32 pm 
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I set up my .22 trap indoors, hung up a target at 10 yards, and proceeded to shoot my AA MPR 400 FT indoors. What a treat.

Ecstasy aside, I used the first mil dot below the crosshair, and adjusted my scope so that I hit dead on at 10 yards with this view. My reasoning was that this summer most of the targets I missed were at short range, so if I sighted in for short range on the mil dot, then found the range at which my pellet was hitting when viewing on the crosshair, I could probably hit more reliably overall.

Anyone else done this? And what might I expect my sight-in range with JSB's to be on the crosshair? I hope I'm not making the experts wince! :mrgreen:

Thanks! :D


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 Post subject: Re: Mil dot question
PostPosted: Sat Dec 15, 2012 9:15 pm 
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Location: SW Ontario:Canada
If you know what your velocity is, Chairgun will give you the info.


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 Post subject: Re: Mil dot question
PostPosted: Sat Dec 15, 2012 9:20 pm 
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Location: Coalmont BC
It depends on if your MilDots are accurate at the magnification of your scope as you were using it when you sighted it at 10 yards....

Bob

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 Post subject: Re: Mil dot question
PostPosted: Sat Dec 15, 2012 10:09 pm 
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Unfortunately, Chairgun doesn't work on Linux. Otherwise, I'd just use it. I think my velocity is around 780 fps with the JSBs. Just by hand, I think it'd be around 28 yards????


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 Post subject: Re: Mil dot question
PostPosted: Sat Dec 15, 2012 10:11 pm 
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rsterne wrote:
It depends on if your MilDots are accurate at the magnification of your scope as you were using it when you sighted it at 10 yards....

Bob


Yes - I shoot everything at about 7 power - I just can't seem to use much more, so I guess I'll actually have to check it out in the field. But that's gonna be a few months away judging from this snow we got!!!! :(


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 Post subject: Re: Mil dot question
PostPosted: Sat Dec 15, 2012 10:31 pm 
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Set up a piece of graph paper at 10 yards, and measure the distance spanned by the MilDots at the power you are using (7).... If the MilDots are accurate at 10X, then at 10X they would be 3.6" at 100 yards, or 0.36" at 10 yards.... At 7X they should be 0.36 x 10 / 7 = 0.51".... If your scope is 10 MilDots from post to post, then that should be 5.1" on the graph paper....

Assuming all that to be the case, then if you are 1 MilDot low at 7X at 10 yards, you are 1/2" low.... With JSBs at 780ish, your POI won't quite ever get to zero.... One half MilDot low at 10 yards should give you a near zero of about 13 yards and a far zero of about 35 yards, and about 0.4" high at 24 yards....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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 Post subject: Re: Mil dot question
PostPosted: Sun Dec 16, 2012 1:28 am 
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Thanks Bob! :D


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 Post subject: Re: Mil dot question
PostPosted: Sun Dec 16, 2012 12:13 pm 
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Location: P.G. B.C.
I think I'd have set up the zero for the 1st dot above the centre of the hairs Gord, thus the crosshairs themselves would be giving a 20 or 25yard zero? We MUST get outside shooting, or maybe I'll get the keys from Taylor for the club-house - a private party?

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Daryl


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 Post subject: Re: Mil dot question
PostPosted: Mon Dec 17, 2012 2:07 am 
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Daryl wrote:
I think I'd have set up the zero for the 1st dot above the centre of the hairs Gord, thus the crosshairs themselves would be giving a 20 or 25yard zero? We MUST get outside shooting, or maybe I'll get the keys from Taylor for the club-house - a private party?


Next Sunday would work.


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 Post subject: Re: Mil dot question
PostPosted: Mon Dec 17, 2012 1:39 pm 
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Depending on the temp, that will work.

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 Post subject: Re: Mil dot question
PostPosted: Mon Dec 17, 2012 3:34 pm 
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Posts: 2102
Location: Greater Napanee, ON, Canada
Gord, you were close to the right setting for the 10 yard dot. Another factor that has to be considered is the scope height, from the centre of the scope to the centre of the barrel, which is fairly easy to find.

I recently shot a match with my FWB300, shooting the JSB 7.9 Express between 715 and 720fps. I have the scope height at 2.25", which makes the holdover at close range considerable, but helps reduce holdover at long range. I set my 10 yard distance at the second mil-dot below the centre crosshairs. What this yielded was most of my shots being taken close to the cross hairs. The close ones from 10 to 15 yards are easy to mark on a crosshair chart that I create and refer to during the match. The 15 yard mark ended up a half mil-dot below the crosshairs and the 20 yard setting was just a bit above the crosshairs. I shot everything from 22 to 32 yards holding down about a half mil-dot. The 40 yard dot was one down from centre, the 45 about 1.5 down and the 50 was two dots down, same as the 10 yards mark. The 55 yard setting was at the third dot down.

With you shooting in the 780 fps range with the JSB 8.4s, a 10 yard setting at the first dot down would in all likelihood, put all shots between 10 and 50 yards between one dot up and one dot down. This also assumes you mount your scope high like I have. I am also assuming that you are shooting in the hunter class and would encourage you to work hard to use the 16X magnification you are allowed in this class or as close to it as possible.

Programs like Chairgun and those like it are useful, but I have never found them to be completely accurate with the scope I use. They can put you in the ballpark, but nothing is better than getting out and confirming your aim-points, plus it is a lot more fun.

Have fun

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Tim
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