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Using chronograph data to determine the best load????

 
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  #8  
Old 12-27-2005, 07:26 PM
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Re: Using chronograph data to determine the best load????

Bart,

I've read much of your stuff over the years. As I say, you're a wealth of information. For any who haven't seen Bart's stuff, here's a page with much of his commentary on it: http://yarchive.net/gun/index.html

Dan
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  #9  
Old 12-27-2005, 07:41 PM
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Re: Using chronograph data to determine the best load????

[ QUOTE ]
I use the ladder method to ID nodes by both grouping on paper and chrono results. Guess what, they normally match up, when a close powder charge range groups on a ladder it will also group very closely on velocity on the chrono. I can pick the tuning node in the MV range I want and normally pick a weight in the middle of the node to take care of any variances with temp or pressure spikes.


[/ QUOTE ]

That is exactly what I used the chrono for. I guess I could have got caught up w/velocity and took the load that was shooting almost 3000 fps, but I saw the wide node between 2830 and 2870 . I loaded 85 gr of Retumbo behind the 240 @ 2850 fps and the rifle shoots .25 MOA @ 100 yds.

I'm not sure of the group sizes @ longer ranges yet, but can tell you I nailed two consecutive milk jugs @ 950 yds and a whitetail @ 503 yds. I'm going to have to agree w/BountyHunter on this one. I believe a chrono can be used to find accuracy nodes as I did w/this rifle. Just remember that accuracy is the first priority, not speed.
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  #10  
Old 12-27-2005, 08:39 PM
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Re: Using chronograph data to determine the best load????

i have shot competitive 1000 yard benchrest.(its been a while though).but in my experience a chronograph's extreme spread will let you know if your case prep and things are in line.if not your loads will be all over(velocity).if your extreme spread is too much you might verticle string shots at long range.what are the "fella's" thoughts on this?
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  #11  
Old 12-27-2005, 08:42 PM
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Re: Using chronograph data to determine the best load????

Most of the time you arenít going into load development and testing ďblindĒ. By that I mean that you usually have some idea as to what loads have been used and what velocities have been attained with those loads, and what will probably be the range in which you will find a useable powder charge.

All chambers and barrels arenít created equal. The load that gives certain results in a barrel and chamber that has most of the dimensions on the loose side will give entirely different results than the same load in a combination that has specs on the tighter side. The chronograph allows you to track the velocities and you can keep track of whether they are following the charge increases like they should.

Most people canít afford pressure testing equipment but just about everyone can afford a chronograph. Sometimes pressure signs may not show up as quickly and easily in a custom action using quality brass, but the velocity of each shot shows up each and every time a bullet goes down range.

Long range shooting would be much more difficult if done without a chronograph. Ending up with large velocity spreads and not knowing it would just drive you crazy when you start getting vertical stringing at extended ranges. Track it with the chrony and you know as soon as it starts to go south on you.

I have also found that usually the velocity results closely track the accuracy results of my load testing. I also base all of my final load decisions on the most accurate load, not the fastest load. I believe that you will find that the vast majority of the long time shooters on this site will choose the most accurate load every time, and not the fastest. Speed is just another parameter that needs to be documented and tracked.

What Iím saying is I consider the chronograph to be one more tool that gives me additional data to help me keep track of load development and testing both in cold weather and hot weather. The more data you have to make your decisions, the more accurate the decisions will be. Why would you not want every available bit of information you can get your hands on?
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  #12  
Old 12-27-2005, 09:37 PM
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Re: Using chronograph data to determine the best load????

I think chronographs are great for helping to plot trajectories and estimate energy, but not for deciding on which load to use.

If the shots are stringing vertically at 1000 yards, it doesn't matter what the chronograph says.

And if the shots are nesting nicely at 1000 yards, it doesn't matter what the chronograph says. [img]/ubbthreads/images/graemlins/smile.gif[/img]


Dan
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  #13  
Old 12-27-2005, 09:46 PM
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Re: Using chronograph data to determine the best load????

30-06 Boy, you're right. Muzzle velocity spread will cause more vertical shot stringing if it's too much. All one has to do is look at down range drop tables for your bullet at different muzzle velocities to figure this out. Example, a .30-06 with 100 fps muzzle velocity spread will have vertical stringing at 100 yards of just under 2/10ths inch. At 1000 yards it'll be almost 40 inches.

Good long range shooters will notice this without a chronograph 'cause their shots won't hold elevation.

Then there's the issue that no two people will get the same muzzle velocity with the same rifle and ammo. There can be 80 to 100 fps difference caused by how they hold the rifle.
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  #14  
Old 12-28-2005, 08:30 AM
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Re: Using chronograph data to determine the best load????

[ QUOTE ]
Then there's the issue that no two people will get the same muzzle velocity with the same rifle and ammo. There can be 80 to 100 fps difference caused by how they hold the rifle.

[/ QUOTE ]

What??? I'm no expert, but how could this possibly make any difference? The same powder charge, the same primer, the same brass, the same chamber, the same bullet, and the same bbl. I'm not buying this. There is no way one person's "holding the rifle different" can make the internal ballistics of the rifle change.
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