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Need help with "true velocity" for a drop chart

 
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  #15  
Old 07-31-2011, 07:33 PM
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Re: Need help with "true velocity" for a drop chart

Kudu, you are correct. I run the numbers on exbal and I used the .659 G 1 BC I always have for the 180 VLD. I cant get the two ranges to woek out perfectly.

I used a corrected 5.75 moa for 465yds

and 16.5 moa for 753 yds. to correspond with your high and low groups.

I suggest shooting again at these two distances and see if you are on using the 5.75 and 16.5 moa. If indeed you are spot on with these numbers we need to look at the scope tracking values and varify it is returning to zero as well.

In fact, I would start with a zero check at 200 to confirm it is still on.

Jeff
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  #16  
Old 07-31-2011, 07:48 PM
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Re: Need help with "true velocity" for a drop chart

At least its not just me. That will be this weeks project.
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  #17  
Old 07-31-2011, 07:55 PM
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Re: Need help with "true velocity" for a drop chart

Quote:
Originally Posted by kudu View Post
At least its not just me. That will be this weeks project.
I ran it on exbal / Nightforce program and it does not give. It will be interesting to see if it still zeroed. 1 moa on a zero will toss ya off at one end or the other.

Jeff
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  #18  
Old 08-01-2011, 01:26 AM
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Re: Need help with "true velocity" for a drop chart

Quote:
Originally Posted by kudu View Post
I understand knowing your gun, but mathematically there must be something I'm doing wrong here.
I doesn't seem practical to shoot a drop chart at every possible elevation combination that I might have (1000 ft for Alaska moose, 2500 ft for Arizona Deer, 5000 ft for Idaho deer, 6500 ft for Wyoming antelope and 8000 ft for elk, then compound that with various temperature combinations that I might experience. Even if I was able to do that my barrel would be ready to be replaced by the time I was finished.
As an experiment when you get your program set up just for kicks just change the elevation and humidity for everything you say in your "quote" above. I think the differences you will find will only be a few inches which will keep you in the kill zone of the animal you will be hunting. The big difference comes in when you shoot up and down hill at big angles.

I sighted in my rifle at about 800 feet in elevation dead on at 200 yds. Then when I got to North East Wyoming I checked it again at 4,500 feet at 200 yds. and it was less than 1/2" different with the temperature and humidity about the same in both Georgia & Wyoming.

joseph

PS: Why do you think that Huskemaw and others sell so many scopes that have a custom turret made for your drop chart? It will only cost you about $100 to get one for your scope. Try one and you will never look back. But be sure to shoot at different distances with YOUR rifle and MEASURE what the drop is from your ZERO. DO NOT USE a program to get the drop measurements. Every rifle shoots differently.

Last edited by joseph; 08-01-2011 at 01:56 AM.
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  #19  
Old 08-01-2011, 07:51 AM
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Re: Need help with "true velocity" for a drop chart

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Originally Posted by joseph View Post
Why do you think that Huskemaw and others sell so many scopes that have a custom turret made for your drop chart? It will only cost you about $100 to get one for your scope. Try one and you will never look back.
I have tried them long ago. You are right about one thing. I never looked back, I loked forward. Engraved turrets limit you... Period!

But never the less the problem and reason he started this thread needs to be found and worked out first. A custom turret would not do any good if there in another mechanical problem.

Jeff
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  #20  
Old 08-03-2011, 11:08 PM
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Re: Need help with "true velocity" for a drop chart

Problem solved! It was the scope. I went shooting yesterday and was getting good data (although I had to re-zero as the scope was off about an 1/2 moa at 200 yards. Pulled out the chrony. Then shot 350 and 465 yards. The chrony and calculated velocities were close (off by about 50 fps). Close enough that I was feeling good. Then pulled up at 750 yards and using the numbers obtained nailed a 4" target! Then shot again 3 times and completely miss the 18x24" steel plate. :( The gun wasn't dropped, miss handled or anything similar. I come back to 200 yards and I am 1 MOA high and 3 MOA to the left.
Came home and removed scope and epoxied the bases down, and remount. Today it shoots decent groups (just under MOA) and it was consistent through all ranges and the calculated velocities are reproducible.
Thanks for the help.
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  #21  
Old 08-04-2011, 08:23 AM
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Re: Need help with "true velocity" for a drop chart

Good for you!! It is a good idea to keep an eye on that zero. Like we talked before a scope not returning to zero will really mess you up. I hope you have it fixed, but I have had two Leupold VXIII's do this to me in the past 4 or 5 years. In fact, both in the same season. Leupold has great warranty, but I choose to not use them anymore. Anyhoot, glad you nailed it down.

Jeff
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