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Dope inconsistancy

 
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  #15  
Old 01-05-2014, 12:29 PM
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Re: Dope inconsistancy

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Originally Posted by Greyfox View Post
Given you scope is OK, and there are no conditions like wind effecting the trajectory, I would expect the answer lies in the BC/velocity settings. The only problem is that it would take a fairly large adjustment to the BC to effect the amount that you are off at 500 yards. The issue is more likely an error in both BC and velocity. The Berger/Litz BC's are generally accurate and would unlikely require the amount of correction to bring your 500 yard impact down. Having had a similar issue a few years ago I found that I solved the problem by first recording the current dopes. Next, adjust your velocity in the ballistic program, in your case, higher so your impact at 500 yards is corrected. Your program will now show your 700-1000 yards dopes low. Now adjust your BC lower to try and replicate the values of your original dopes for the longer ranges. I may take some trial and error. IMO
This is something ive considered, the only thing that bothers me is that shooting over my chrono yeilds velocities that work out really close to my dope. So im not sure where to start.
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  #16  
Old 01-05-2014, 12:32 PM
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Re: Dope inconsistancy

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Originally Posted by Canadian Bushman View Post
This is something ive considered, the only thing that bothers me is that shooting over my chrono yeilds velocities that work out really close to my dope. So im not sure where to start.
what chronograph are you using?

I think I would move to 700 or 800 yards and shoot 2 or 3 groups letting the barrel cool and see what that yields for sure.

At 500 is it just cold bore shots going high or is this a center group measurement?

Jeff
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  #17  
Old 01-05-2014, 01:26 PM
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Re: Dope inconsistancy

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Originally Posted by Broz View Post
what chronograph are you using?

I think I would move to 700 or 800 yards and shoot 2 or 3 groups letting the barrel cool and see what that yields for sure.

At 500 is it just cold bore shots going high or is this a center group measurement?

Jeff
Im using a beta chrony thats been shot twice so i have no problem throwing out data i recieve from it, i just think the fact that it matches so much of my data is more than coincidence.

My cold bore shot is eerily consistent with rifle always grouping very well with subsequent shots.

Just two weeks ago i shot a 3" 3 shot group centered on point of aim at 741yds with this same load, using load and weather conditions in shooter.

Last week i shot two feral hogs at 635yds and the bullet hit about 2-3" from point of aim, again with shooter plotting conditions.

This tuesday i got a second round hit at 910yds that was 6" high again with shooter.

And this is also the load that i use for 1k yd ftr, and always lands between 36-37 moa for the entire string at the range shooting due north. And we typically fire 60 rounds a match.
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  #18  
Old 01-05-2014, 01:34 PM
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Re: Dope inconsistancy

My chrony does tend to give me readings about 10-20 fps faster then the mv that works in shooter, but at the ranges i shoot most and the average accuracy im able to hold this difference doesnt account for much.

My average es for this load is around 20 to 25 fps.
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  #19  
Old 01-05-2014, 01:45 PM
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Re: Dope inconsistancy

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Originally Posted by bigngreen View Post
Are you using a G1 or G7 BC, are you on out to a 1000 yards?
Im using the G1 bc. Ive run the same data with the G7 and its identical.
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  #20  
Old 01-05-2014, 02:02 PM
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Re: Dope inconsistancy

Well you already know the data from a shooting chrony is questionable. As is true with the 3 I own. But this still does not answer the question of why 5" high at 500 and spot on at 750? I am just thinking and asking questions that come to mind. If your 500 yard data is center group and not cold bore it eliminates the barrel stress, stock and bedding idea's. I truly feel there is a glitch somewhere. You stated it is not in scope tracking so I am at a loss. But we have all set up many rifles, I would like to know for sure why this one is off a full moa at only one distance.

Do you have the powder temp data area of the program zeroed? I have seen some wrecks from bad data there.

If I come up with an idea I will post again.

Jeff
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  #21  
Old 01-05-2014, 02:50 PM
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Re: Dope inconsistancy

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Originally Posted by Broz View Post
Well you already know the data from a shooting chrony is questionable. As is true with the 3 I own. But this still does not answer the question of why 5" high at 500 and spot on at 750? I am just thinking and asking questions that come to mind. If your 500 yard data is center group and not cold bore it eliminates the barrel stress, stock and bedding idea's. I truly feel there is a glitch somewhere. You stated it is not in scope tracking so I am at a loss. But we have all set up many rifles, I would like to know for sure why this one is off a full moa at only one distance.

Do you have the powder temp data area of the program zeroed? I have seen some wrecks from bad data there.

If I come up with an idea I will post again.

Jeff
Temp data isnt completely ironed out, and could be questioned but i have been narrowing it down this last year and feel im getting very close.

My problem here is in shooter the temperature variation is linear and im not sure the relationship between velocity change and temp is linear. So i dont know how close is as close as ill be able to get.

There are a few things i dont understand and have in question. Perhaps they could be related to my problem.

Bullet B.C. In relation to MV - ive always trusted bergers published B.C., dont know any better.
Scope height - measuring on canted base
Copper fouling - rifle seems to shoot high (faster) as fouling increases - obvious in rising zero over 70-100 shots.
Factory Barrel - very rough, and copper fouls quickly.
Semi-New Nighforce nxs - seems to track and hold zero identically to last nightforce, but im always suspicious.
Shooter error - im currently struggling with consistancy in trigger control, shouldering the rifle the same with equal pressure, controlling recoil the same way each time i shoot, and managing my reloads to shoot consistent MV, ES, and accuracy.
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