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July 15, 2011, 05:20 PM | #1 |
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Are The Hodgdon Powder Charts A Bit "Low"?
I am testing out some .38 Special loads I finished this last week and they are consistantly reading close to 100 FPS lower than the Hodgdon chart using the primer, powder and bullet weights recommended. Are the charts aimed at "safe" levels or is it my electronic weigh scale? I test the scale with the test weight before every use and it passes every time. Thanks...
PS-On these .38 Specials I am using the 110gr. XTP bullets and 4.6 gr. of the HP-38 just for plinking and they sure are anemic! At 25 yards they drop about 1 foot though centered directly below the bulls eye. I am using a bench rest with my Dan Wesson .357 with 6" barrel. |
July 15, 2011, 05:28 PM | #2 |
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You would have to using the exact some gun with the exact same components and the exact powder lot to get the exact same results as they got.
I have found their data to be spot on as far as safe pressures go. |
July 15, 2011, 06:45 PM | #3 |
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No, I think they publish their findings for Minimum and Maximum ....based on the best data they have.
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July 15, 2011, 07:51 PM | #4 |
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Some loads are tested using test barrels, some using 6" - if you are using a 4" for example - it will be less than their results
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July 15, 2011, 08:15 PM | #5 |
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The actual chronographed velocity will nearly always be lower for the consumer with a mass produced gun than the lab with a pressure test rig.
PV (Pressure & Velocity) test barrels are of minimum chamber and bore dimensions so as to give the maximum pressure for the combination, so you don't overload a standard gun. The high velocity is just an advertising bonus. Some revolver calibers are tested in a vented barrel to simulate the cylinder gap, some are shot in long straight barrels. No way to know if they don't tell you. Also, your 110 grain bullets are striking low not because the velocity is lower than advertised, it is because they are lighter than standard. They don't induce as much recoil and barrel lift while still traveling down the barrel as a standard 158 grain bullet does. |
July 15, 2011, 08:40 PM | #6 |
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Fyi, if you click on the print option on the data website, it will tell you the gun they used for testing.
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July 17, 2011, 08:30 PM | #7 |
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JWs spot on for the low POI, shoot a slower load and the POI will be higher, as will a heavier bullet. Fixed sight revolvers sometimes take some regulation and/or may only hit POA with one bullet, one load. Hodgdon seems to play it straight with good minimum chambers and test barrels. They monitor pressures found with their equiptment, and report the loads up to maximum pressure. Sometimes velocities are load compared to some reported factory loads and they may be low compares to "street" loads, but I think they are reporting what they have found. Revolver velocities can vary all over the planet due to the wide range of cylinder, throat, cylinder gap, forcing cone and barrel dimensions.
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July 17, 2011, 09:01 PM | #8 |
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I'm reminded of a required engineering class, Stress Lab, from many years ago. The class was divided into teams and we tested all sorts of materials/assemblies (typically to failure). For supposedly identical tests, the data varied from team to team. The same thing happened in the university physics labs. I suspect it occurs in ballistics labs, too. Toss in a standard safety factor and litigation avoidance attorneys, and it's no wonder you may not see signs of high pressure at the maximum listed loads.
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July 17, 2011, 10:13 PM | #9 |
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Imagine you wanted to make money.
Print a load book with fantastic velocities, slow powders, and the case nearly full of powder. What can go wrong? Someone on some forum somewhere going to complain? HA!
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