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  #1  
Old 01-14-2004, 11:24 PM
Critch Critch is offline
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Angry 38 Super Auto vs 357 Magnum

I'm a little confused. My number 13 Speer manual shows the 38 super being able to propel a 125 gr bullet at 1255 fps with 9 grs of HS-7, but the 357 magnum uses 13.3 grs of HS-7 and only goes 1169 fps. I realize that the 357 can handle heavier bullets overall, but can someone explain the physics of that example? It doesn't make sense to me.

The fact that a 38 super auto carries more rounds than a 357 magnum revolver could be a good selling point for CCW.

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  #2  
Old 01-15-2004, 02:05 AM
gd357 gd357 is offline
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What were the lengths of the test barrels used to come up with those values? Possibly, the gas that escapes between the cylinder and the barrel could have something to do with it, but that wouldn't explain the total difference, unless the powder wasn't completely burned when the bullet left the barrel of the .357.....

gd357
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  #3  
Old 01-15-2004, 06:36 AM
MarkL MarkL is offline
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Is that the max for that powder in the 357? If not, I'm guessing the larger case capacity of the 357 means a lower pressure is generated. Are those two loads for the same bullet weight?
  #4  
Old 01-15-2004, 06:56 AM
Mr. 16 gauge Mr. 16 gauge is offline
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My guess would be cylinder gap.
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  #5  
Old 01-15-2004, 07:56 AM
reload reload is offline
 
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38 super-.357

Quote:
Originally posted by Mr. 16 gauge
My guess would be cylinder gap.
Critch, When you shoot the .38 super at that velocity you are at about break point. You will lose about half of your cases. It isn't practical. If you use 296 in the .357 you can shoot 125 grain hp bullets a lot faster than that , but again using new cases you most likely won't be able to do it a second time with the same brass with the tight crimp to develop the velocity. Good Luck
  #6  
Old 01-15-2004, 08:07 AM
Critch Critch is offline
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I don't have my manual with me here at work to look up the test barrel lengths. The test barrels could make a difference, I never thought about the higher pressures in the 38 Super. That could make a difference, as well as the cylinder gap.

I've reloaded for a number of years, but never 38 Super, I like the stats on the round, but some reloading tables don't always make sense.

Do those higher pressures also account for 308's going faster with the same bullet than 30.06's with higher powder charges?
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Old 01-15-2004, 09:35 AM
gd357 gd357 is offline
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I've never seen a .308 shoot the same bullet as fast as a 30-06 when they were both loaded to their respective potential (but there's a first time for everything). The .308 is generally regarded well because it has better inherent accuracy potential than the 30-06.

gd357
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  #8  
Old 01-15-2004, 09:48 AM
buckhunter buckhunter is offline
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It may have to do with product liability. There are a lot of junk 357's out there whereas the 38 Super's I have seen "appear" to be better quality guns. Just a shot in the dark. Now Rocky really tell us why.
  #9  
Old 01-15-2004, 10:01 AM
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Rocky Raab Rocky Raab is offline
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The real reason is case volume.

The 38 Super, with that bullet seated, leaves very little room in the case. The 357 Magnum is not only a longer case, but is designed to handle longer bullets. So with the same bullet as the 38 Super, there's much more volume in the case.

The result is that the 357 will take more of the same powder to develop anywhere near the same operating pressure. But even that added powder can't make up for the loss of pressure through the cylinder gap. In addition, because both are straight-sided cartridges, the combustion volume increases almost exponentially as the bullet moves. That drops pressure so fast that the powder cannot burn effectively after only a very small length of bullet travel. (That's the expansion ratio of the round)

As an interesting sidelight, I have actually fired factory 38 Super ammo in a 357 Mag revolver (yes, it can be done - safely - as long as the ammo chambers. Some 357 chambers are too tight)

I got 1200 fps with the 38 Super ammo (it had 130 FMJ bullets). Factory 125-gr 357 ammo in that same gun develops over 1500 fps.
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