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Extreme Velocity Spread Question - I'm perplexed

 
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  #8  
Old 06-26-2011, 02:19 PM
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Re: Extreme Velocity Spread Question - I'm perplexed

Quote:
Originally Posted by Mikecr View Post
I can't think of anyway neck lube would have an affect.
What difference was there in brass size from load development to validation loads?
I did 200 rounds of brass in one batch. The 5 shot 19 fps spread and the 64 fps spread were both out of that batch. 3 firings on each case.
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  #9  
Old 06-26-2011, 02:28 PM
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Re: Extreme Velocity Spread Question - I'm perplexed

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Originally Posted by phorwath View Post
It sounds like you're being very careful and methodical with your load development, so I suspect you already know what your next step is. Dry neck lube another 5 rounds and see what kind of ES you get. If it matches the first 5 shots, then you'll know what the story is. If it doesn't match, then it's time for more load development - or another chronograph.

With only one chronograph, it's impossible to know if you're getting credible data or not, because you've got nothing to compare to. I run three chronographs concurrently to reduce the odds of being mislead with data from a single chronograph that might be acting up. The odds that more than one will spit out bad data on any single shot fired aren't very high. At the minimum, I can qualify the credibility of any velocity data obtained when the three chronographs aren't in close agreement.

Let us know what you conclude if you're able to figure it out.
That's a good idea! Bet you get a few looks at the range. I use the PV-21

PVM-21 Chronograph Details

i always thought that a 2nd (or in your case a 3rd) chronograph would be helpful.

Here's the data that i wrote down from the first to 13th shot:

64 FPS ES:
  • 2,809
  • 2,820
  • 2,812
  • 2,808
  • 2,836
  • 2,798
  • 2,792
  • 2,815
  • 2,809
  • 2,810
  • 2,797
  • 2,810
  • 2,772

19 FPS ES from 2 weeks ago:
  • 2,828
  • 2,825
  • 2,809
  • 2,826

THANK YOU ALL FOR YOU IDEAS.
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  #10  
Old 06-26-2011, 02:30 PM
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Re: Extreme Velocity Spread Question - I'm perplexed

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Originally Posted by trebark View Post
No answers from me either, just a few questions...

what was rate of fire for each session? it's possible that a heated barrel would go 'faster'

where did the velocities from your first tests fall in the second session? (low end, middle, high end?)

In the end, the odds are your first session was not a sufficient number of data points to truly make a determination about the true ES of the load.
I only shoot 5 shot (or 3 shot) groups and then let the barrel cool to a point where it isn't warm to the touch or at least not hot.
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  #11  
Old 06-26-2011, 02:32 PM
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Re: Extreme Velocity Spread Question - I'm perplexed

One last thing. Brass was all the same manufacturer (Remington) and all primers are CCI 250 magnum primers.
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  #12  
Old 06-26-2011, 02:41 PM
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Re: Extreme Velocity Spread Question - I'm perplexed

You didn't, or I didn't catch it, mention accuracy. I would recommend shooting at least 200 yards, 300 would be better.

Seeing as you appear to be very meticulous let me recommend trying this. I wouldn't recommend it to anyone that was now very particular regarding reloading.

With that same powder, maybe a little less of a charge, and same brass and primer jam that bullet well into the lead. That is drive it so much that the bullet is actually pushed into the case by the rifling. I did this by mistake on 5 reloads. Every thing was better. Pressures were not excessive, ES dropped significantly and group size shrunk to extremely pleasing levels.

The cartridge is a 338 RUM.

Another choice is a different powder......
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  #13  
Old 06-26-2011, 02:43 PM
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Re: Extreme Velocity Spread Question - I'm perplexed

Quote:
Originally Posted by shepardsonp View Post
That's a good idea! Bet you get a few looks at the range. I use the PV-21

PVM-21 Chronograph Details

Here's a link to a Thread with some photos of the setup, and some data collected from the setup. I've run dual chronographs in tandem for a number of years. I expanded that setup by adding an Oehler 35P last Fall. When I chronograph now, each bullet flies over 7 skyscreens.

New Oehler 35P, New skyscreen rail, First Test Data

Last edited by phorwath; 06-26-2011 at 03:02 PM.
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  #14  
Old 06-26-2011, 02:55 PM
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Re: Extreme Velocity Spread Question - I'm perplexed

Dry neck lube will make the difference, I gave it a try after reading some one doing it, don't quote me but I think it was Carlock with a 338Edge. I don't use it anymore and started annealing to maintain consistent bullet release.
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