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Old February 22, 2013, 05:22 PM   #1
SL1
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Join Date: November 8, 2007
Posts: 2,001
Issues matching Nosler .357 Mag data with QL

I have been spending some time trying to match velocity vs charge weight data in various manuals using the QuickLOAD program.

Some of the data in the latest Nosler manual (#6) for the .357 Magnum cartridge looks suspect. I tried calling Nosler and speaking to a "tech" but found that he had no interest what-so-ever in considering that some of their data might not be correct or might not be published correctly.

So, I am putting it out here to see what others think.

Here is a graph of the data provided for the 158 grain JHP:



As you can see, the data for all of the faster powders, except SR-4756, show a reasonable velocity increase with increasing powder charge, while the slowest powders do not. (SR-4756 is not quite as bad as the slow powders, but also looks weird.)

Matching the fast powders that I have in the QuickLOAD data base (only AA #5 and #7) showes fairly decent agreement with the data when just using the default values in QuickLOAD:



However, trying the same thing with the two slow powders does not:



The lowest dotted lines are the QuickLOAD results using the default values. The middle dotted lines are the QuickLOAD values with the case capacity reduced to produce the SAAMI max pressure for the top charge of 2400 powder, with the same capacity used for W-296. The upper dotted line is with the default case capacity, but the Burning Rate Factor for each powder has been increased to produce the SAAMI max pressure for the top charge.

What is obvious in these graphs is that the slopes of the 2400 and 296 plot lines are MUCH different for 2400 and 296 than for the faster powders, and that QuickLOAD matches the faster powders pretty well, but no adjustment of the QuickLOAD parameters comes close to matching the slope of the slow powders.

My guess at the cause of this situation is that the Nosler ballistician's chronograph might have been reading the shock waves from the fireballs produced with the slow powders rather than the passages of the bullets.

The data for these powders is a follows. (It was shot with an 8.3" H&S Precision barrel):

2400 11.3 grains 1480 fps
11.8 grains 1500 fps
12.3 grains 1520 fps

296 13.8 grains 1520 fps
14.3 grains 1530 fps
14.8 grains 1540 fps

Another thought is that these charges seem rather light for these powders in this cartridge with this weight bullet. Perhaps the powders are not burning well.

What do others think?

SL1
Attached Images
File Type: jpg Nosler 357 Mag data.jpg (20.9 KB, 56 views)
File Type: jpg QL match fast p.jpg (20.8 KB, 55 views)
File Type: jpg QL match slow p.jpg (25.3 KB, 58 views)

Last edited by SL1; February 23, 2013 at 09:50 AM.
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