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PostPosted: Mon Jul 07, 2014 7:07 pm 
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Joined: Fri Jun 01, 2007 11:36 am
Posts: 2220
Location: Nova Scotia, near Halifax
yup,
so i ran the beloved chair gun program and it said i should hold over one mil dot at 20 yards, but it turned out to be three!!! :shock:
so i figured i didn't have the generic mil dot calibration right.

here are the blanks i need filled:

full mil-dot = ?

@ magnification = ? (no where in the manual does it say what power to use)

range= ?

vertical distance = ?

i know the scope has 1/4 moa that's about it.
there are nine mill dots either side of the cross hairs
utg 4-16x40

thanks for your help. i really want to get this dallied in.

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my other coil is a sub ohm
sub 500 .22 Crosman Phantom 500 open sites
sub 500 .177 Crosman TR77 NPS 4-16x40 UTG
sub 500 .177 Hatsan mod 33 with Quattro trigger open sites


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PostPosted: Mon Jul 07, 2014 7:28 pm 
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Joined: Sun Jul 28, 2013 8:34 pm
Posts: 1155
Location: Vernon BC
Sorry, I don't understand your "fill in the blank" questions? If calibrating your scope, you can use any magnification you want, preferably the magnifications you shoot at most (e.g 5x and 10x).

Try watching these two videos, part 1 and 2. The chairgun used in the video is obviously outdated but it still gives you the general idea.

I've done it this way and now can make shots out to 95 yards with my trusty 'scope cap cheat sheet' and rangefinder.

Your problem may have been due to not entering the correct/full information such as pellet b.c, scope height, velocity etc. Ths vdeo may help you as it did me when calibrating my scope and air rifle.

Part 1
https://www.youtube.com/watch?v=hPoCW9kYAkc

Part 2
https://www.youtube.com/watch?v=DglJYVIAKnY

Only differences I did was make a bit more accurate measure of center of scope to center of barrel..


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PostPosted: Wed Jul 09, 2014 6:54 pm 
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Joined: Fri Jun 01, 2007 11:36 am
Posts: 2220
Location: Nova Scotia, near Halifax
yea,
i think my pellet b.c, scope height, and velocity ect is correct. (scope high is close but i will tune that asap!!! thanks for reminding me!! )

i'll watch the videos again.

i just can't it to line up to where it should be. the POI and hold over/ under in MIL_DOTS.

the value of poi makes sense, but the mil dots are completely wrong. :evil:

l love this program and would love to have it working to it's fullest.

_________________
my other coil is a sub ohm
sub 500 .22 Crosman Phantom 500 open sites
sub 500 .177 Crosman TR77 NPS 4-16x40 UTG
sub 500 .177 Hatsan mod 33 with Quattro trigger open sites


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PostPosted: Wed Jul 09, 2014 8:39 pm 
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Joined: Sat Nov 03, 2007 4:19 pm
Posts: 8989
Location: Coalmont BC
As you change the magnification on or scope, the apparent distance between the MilDots changes.... You have to input your current magnification into ChairGun....

Bob

_________________
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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PostPosted: Thu Jul 10, 2014 5:27 pm 
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Joined: Fri Jun 01, 2007 11:36 am
Posts: 2220
Location: Nova Scotia, near Halifax
Image

btu i chronoed the gun to the valve shown
i am using jsb exact diabolo 8.44 grain with cronoed at 468

what am i doing wrong?
my shots are down 2 1/2 inches at 20 yards. i am zeroed at ten yards (all day long)
according to chair gun i should bee in the kill zone.
what the ....????

if you need more info or pic just ask. i have to get this figured out.

side note: i can change the values in the mil-dot calibration but they won't stick.

so, in summary:
my poi is of by 2.5" a20 yards


uggg?? why?? :drinkers:

_________________
my other coil is a sub ohm
sub 500 .22 Crosman Phantom 500 open sites
sub 500 .177 Crosman TR77 NPS 4-16x40 UTG
sub 500 .177 Hatsan mod 33 with Quattro trigger open sites


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PostPosted: Thu Jul 10, 2014 8:31 pm 
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Joined: Wed Feb 17, 2010 6:04 pm
Posts: 841
Location: Nova Scotia
quickreply7789 wrote:
my shots are down 2 1/2 inches at 20 yards. i am zeroed at ten yards (all day long)


I suspect the first POI is off.
Try setting the scope at 10 power, zero at 20 yards and check the POI at 10 yards. If your speed is 468 fps you should have a first POI at 10 yards and a second POI at about 20 yards. Don't worry about mil dots until the rifle shoots near the 10 and 20 yard zeros.


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PostPosted: Thu Jul 10, 2014 9:18 pm 
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Joined: Fri May 04, 2012 9:43 pm
Posts: 236
Location: North of Kenora
I suspect your rifle suffers from barrel "Droop"
You may need a compensating mount to get rid of the drop at 20yds. JMHO
http://www.google.com/url?sa=t&rct=j&q= ... 0081,d.b2U

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PostPosted: Fri Jul 11, 2014 7:28 pm 
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Joined: Fri Jun 01, 2007 11:36 am
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Location: Nova Scotia, near Halifax
ok i will set my poi for 20 yards and see where that gets me.

thanks for your help guys. i have to get this working.
i really appreciate it guys, you have now idea how much!!!!

_________________
my other coil is a sub ohm
sub 500 .22 Crosman Phantom 500 open sites
sub 500 .177 Crosman TR77 NPS 4-16x40 UTG
sub 500 .177 Hatsan mod 33 with Quattro trigger open sites


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PostPosted: Tue Jul 15, 2014 4:55 pm 
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Location: Nova Scotia, near Halifax
ok,
so i set the zero to 20 yards (measured) and the poi at 10 yards (measured) is now 1" high !??!
chair gun says it should be basically zero.
i did set the scope height too.

so what should i do now?


thanks for your continued help with this one.
how can i be a sniper when i can't this working??? 8) :lol: :evil:

do you think i can get the sub 500 mod 33 reach out to a thousand yards, any time soon?? :lol:

_________________
my other coil is a sub ohm
sub 500 .22 Crosman Phantom 500 open sites
sub 500 .177 Crosman TR77 NPS 4-16x40 UTG
sub 500 .177 Hatsan mod 33 with Quattro trigger open sites


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PostPosted: Wed Jul 16, 2014 12:48 pm 
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Joined: Thu Dec 15, 2011 11:24 am
Posts: 331
I've read somewhere (sorry, can't recall where) that the ballistic coefficient of a pellet is an approximation that can vary +/- 15%. Perhaps adjust the BC +/- 15% and see how the new values concur with the old.


Other things to double check (please don't be insulted)

-target centered and level with barrel (i.e. not shooting down from a porch)
-meters are meters and yards are yards (20 meters=21.9 yards)
-scope height is measured from the center of barrel to center of scope
-any wind? Strength and direction easily inputted into Chairgun program


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PostPosted: Wed Jul 16, 2014 1:01 pm 
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Location: Coalmont BC
One additional thing.... If your barrel has significant "droop" the scope will be closer to the barrel C/L than what you measure at the receiver.... You need to project the barrel C/L up to the middle of the scope (about where the turrets are) and use the C-T-C distance relative to the projected barrel C/L....

Bob

_________________
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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PostPosted: Wed Jul 16, 2014 7:10 pm 
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Location: North of Kenora
Chairgun will never work in a gun that's bore is not in line and parallel with the centerline of the scope. If your barrel has "droop" and a droop compensating mount is not used you can play around with BC and mil dots all day long and never change the fact the gun shoots LOW. It will also shoot high at closer ranges if sighted in for a longer range. This seems to be exactly the situation the OP is describing. He needs to shim the scope or get a compensating mount to solve his misalignment problem before he will get reliable results from chairgun. JMHO

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Neil deGrasse Tyson


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PostPosted: Wed Jul 16, 2014 7:42 pm 
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Location: Coalmont BC
I disagree, when you move the reticle, it is no longer on the centerline of the scope, but that doesn't prevent two straight lines being drawn, one through the boreline of the barrel and the other through the IMAGE LINE (Point of Aim) of the scope.... All Chairgun does is subtract the drop at various ranges from the barrel boreline.... Since scopes are virtually always above the bore, and the two lines CANNOT be parallel or you could never sight in your gun, your statement is flawed....

Bob

_________________
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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PostPosted: Wed Jul 16, 2014 9:10 pm 
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Joined: Fri May 04, 2012 9:43 pm
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Location: North of Kenora
Than I guess we will have to disagree.
I realize the barrel and sight line must intersect at some point in order for a scoped rifle to work.
The problem arises when the barrel and sight are pointing in different directions to start with.
How are chairguns calculations for drop supposed to work if the barrel droop is causing the pellet to drop more than velocity decrease and friction are predicted to cause?
An example:
If you shoot a pellet through a gun sighted in at 10yds and the drop over 20yds is predicted to be -1" and -4" at 40yds(just approximate numbers) chairguns predictions will be correct in a gun with parallel bore and sight.
But,
If you shoot the pellet through a drooped barrel that causes 6" of drop at 10yds (an extreme example) and it is sighted in for 10yds,, it will have-12" + the actual 1"(13") drop at 20yds and -24"+ -4"(28") at 40.
There is no way chairgun can take "droop" into account as every gun that has droop has different"droop"
Bore and scope must be close to parallel for the calculations to work.

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"The good thing about science is that its true whether or not you believe in it."
Neil deGrasse Tyson


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PostPosted: Thu Jul 17, 2014 12:03 am 
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Location: Coalmont BC
You didn't use ANY drop at 10 yards, so I will assume you are using POI (ie drop relative to POA) not "drop" for your 1" at 20 yards and 4" at 40 yards.... The bullet, of course, starts to drop as soon as it leaves the barrel.... but I'll use your terminology....

If the gun with the drooped barrel is sighted in, as you say, for 10 yards, and the scope is 1" above the barrel, a line through the scope will be pointing down 7" at 10 yards if the barrel is pointing down 6" OR THE GUN WON'T BE SIGHTED IN AT 10 YDS.... As you state, the boreline (which is where the drop is measured from) will be down 12" at 20 yards and 24" at 40 yards.... A line through the scope (POA) will, however, be down 14" at 20 yards and 28" at 40 yards....Add the "drop" of 1" at 20 and 4" at 40 (relative to the boreline) and you would have the pellet hitting 1" high at 20 yards, relative to POA, and dead on at 40 yards....

In a gun with no droop, where the boreline and the scope centerline are parallel, and the scope is 1" above the barrel, a line through the scope will be pointing down 1" at 10 yards (to sight in the gun), 2" at 20 yards, and 4" at 40 yards, relative to the boreline.... Add the "drop" of 1" at 20 yards and 4" at 40 yards (relative to the boreline), and you have the pellet hitting 1" high at 20 yards, relative to the POA, and dead on at 40 yards.... Looks the same to me !!!

Straight lines are still straight lines.... What WILL change, however, is that the scope will actually be sitting closer to the boreline than it is above the receiver if the barrel has droop than it would in a gun with no droop.... If we take an example of a scope mounted 12" behind the hinge point, on a gun where the top of the receiver is level with the back of the barrel, and the barrel has your 6" of droop in 10 yards (360"), that moves the aft projection of the boreline (6" x 12" / 360") = 0.2" closer to the scope.... If you measure the scope as being 1.5" above what you think is the boreline on a gun where the barrel is parallel to the receiver, you should only use 1.3" to allow for the projection of the boreline being 0.2" higher at the scope location.... That is what I was trying to say in my original post.... Scope height must be measured to the boreline (or it's projection) AT THE LOCATION OF THE SCOPE RETICLE....

Bob

_________________
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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