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What is going on here?

 
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  #1  
Old 09-28-2013, 12:27 AM
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Location: Kamiah, Idaho
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What is going on here?

When I chrono my 300 WM load with the Berger 210 VLD's it averages around 2920 fps. I set the chrono 15 feet from the muzzle. But when I go to the G7 Ballistics Calculator and confirm trajectory at 400 yards it wants to either change the published BC or speed up the bullet to 2985 fps. Which should I trust, my chronograph , the published BC from Berger, or the G7 Ballistics Calculator?
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Old 09-28-2013, 01:25 AM
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Re: What is going on here?

I would trust what your chrono says as long as you're positive your chrono isn't reading muzzle blast.

Other than that, one of the other guys will have to help, as I don't use the G7 ballistics calculator.
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Old 09-28-2013, 07:45 AM
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Re: What is going on here?

I have used many 300 wins with 210 Bergers. A max load of H-1000 will get me just over 2900 from a 28" barrel. Using the Shooter app and the factory BC of .631 it worked out with drops to well past 1000 yards.

Hope this helps.

Jeff
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Old 09-28-2013, 07:47 AM
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Re: What is going on here?

If you put all data into the G7 calculator, it should give you more accurate information.

Something like, attitude, air pressure, humidity, etc...
The chrono will give you the quick answer when you shot on that day.
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Old 09-28-2013, 12:21 PM
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Re: What is going on here?

yur never supposed to say "never".

But, I say, never, never, never, trust the chrono (unless maybe ya paid big bucks for it) UNTIL drop confirms velocity.

The chrono that is usually used will get you in the ball park. Drop validation will get you spot on.


I'd use Jeff's bc value then validate.
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Old 09-28-2013, 02:03 PM
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Re: What is going on here?

Quote:
Originally Posted by royinidaho View Post
yur never supposed to say "never".

But, I say, never, never, never, trust the chrono (unless maybe ya paid big bucks for it) UNTIL drop confirms velocity.

The chrono that is usually used will get you in the ball park. Drop validation will get you spot on.


I'd use Jeff's bc value then validate.
Agreed. It is always about trajectory validation. You do have to do your due diligence in setting up the validation correctly with correct inputs for atmospheric conditions, load data, etc. but once you get that down you almost don't even need a chrono. I have gotten pretty good with just loading for accuracy, guessing on velocity from published load data to get me close, then validating trajectory to determine my drop chart, velocity, and shooter ap inputs.

HTH,

Scot E.
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Old 09-28-2013, 05:08 PM
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Re: What is going on here?

I'd sure use my actual drops . one other thing you need to check , be sure your scope zero , is dead on zero . if the zero is off a little it throws it all off . Jim
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