The Firing Line Forums - View Single Post - Issues matching Nosler .357 Mag data with QL

SL1 · February 22, 2013, 08:14 PM

Buck,

Are you saying that you can subtract a grain of powder from your max 296 loads and only lose 20 fps in velocity from your revolver?

That is what got my attention.

Speer seems to think that you lose 94 fps by subtracting 1.5 grains, and Hornady seems to think that you would lose 50 fps by subtracting 0.8 grains. Those are both equal to 63 fps per grain of 296, both from 6" revolver barrels.

QuickLOAD showes a loss of 108 fps per grain of 296 for the 8.3" barrel.

But, remember, a revolver with a "six-inch barrel" is really more like a 7.6" barrel when you add in the cylinder length. So, the real difference between the test barrel data and the revolver data is the presence of the cylinder gap and the forcing cone.

Speer made a pressure test apparatus for a revovler many years ago, when piezo transducers were relatively new. It showed that the pressure curves were much different in the revolver, with higher peaks and more rapidly reducing pressure after the peak. At least, that was true with the bullets that they manufactured at that time. They found that slightly reducing bullet diameter changed that. Then, they also changed to thick-plated bullets ("Unicor" and "Gold Dot") instead of cup-and-core. But, Hornady bullets are still cup-and-core.

So, I am not seeing anything like this Nosler data from anybody else. That is why I am asking about your personal chrono data, particularly the slope of the line in fps change per grain change.

SL1

February 22, 2013, 08:14 PM	#3
SL1 Senior Member Join Date: November 8, 2007 Posts: 2,001	Buck, Are you saying that you can subtract a grain of powder from your max 296 loads and only lose 20 fps in velocity from your revolver? That is what got my attention. Speer seems to think that you lose 94 fps by subtracting 1.5 grains, and Hornady seems to think that you would lose 50 fps by subtracting 0.8 grains. Those are both equal to 63 fps per grain of 296, both from 6" revolver barrels. QuickLOAD showes a loss of 108 fps per grain of 296 for the 8.3" barrel. But, remember, a revolver with a "six-inch barrel" is really more like a 7.6" barrel when you add in the cylinder length. So, the real difference between the test barrel data and the revolver data is the presence of the cylinder gap and the forcing cone. Speer made a pressure test apparatus for a revovler many years ago, when piezo transducers were relatively new. It showed that the pressure curves were much different in the revolver, with higher peaks and more rapidly reducing pressure after the peak. At least, that was true with the bullets that they manufactured at that time. They found that slightly reducing bullet diameter changed that. Then, they also changed to thick-plated bullets ("Unicor" and "Gold Dot") instead of cup-and-core. But, Hornady bullets are still cup-and-core. So, I am not seeing anything like this Nosler data from anybody else. That is why I am asking about your personal chrono data, particularly the slope of the line in fps change per grain change. SL1