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Rifles, Reloading, Optics, Equipment
Reloading
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<blockquote data-quote="Littlehud" data-source="post: 2106992" data-attributes="member: 85418"><p>I know there are some very knowledgeable people on this forum, so I will put this out here. </p><p></p><p>I am a bit confused about some of the load data I am seeing for different powders. Using the same bullet and cartridge, but different powders, I see different velocities and pressures, but not exactly what I expected. As an example, I have the load data for a .270 Winchester for IMR 460 (101), Hodgdon Hybrid 100V (128), Winchester StaBALL 6.5 (129), and IMR 4831 (132) powders. The numbers in parenthesis are the rank number in the burn rate chart.</p><p></p><p>The confusing part is this: H 100V and StaBALL 6.5 have similar burn rates, being #'s 128 and 129 on the chart. They give similar velocities with similar pressures, just as one would suspect. However, 4064 and 4831 also give similar velocities with similar pressures but are far apart on the burn rate chart at #'s 101 and 132 respectively. Why so similar when the burn rate is so different?</p><p></p><p>The other thing that confuses me even more is that looking at maximum loads for the different powders, 100V and 6.5 show 62,300 PSI while 4064 and 4831 both show just under 51,000 PSI. How can there be so much difference for max loads? Why couldn't you use more powder with 4064 to increase the pressure to 62,000 and get higher velocities? There's obviously more to the equation here.</p><p></p><p>270 WINCHESTER</p><p>Case: Winchester</p><p>Twist: 1:10.000"</p><p>Primer: Winchester LR, Large Ri e</p><p>Barrel Length: 24.000"</p><p>Trim Length: 2.530"</p><p>BULLET WEIGHT</p><p>140 GR. SFT SP</p><p></p><p> Starting Loads Maximum Loads</p><p></p><p>Powder Bullet Diam. Grs. Vel. (ft/s) PSI Grs. Vel. (ft/s) PSI</p><p></p><p>IMR 4064 0.277" 42.0 2,608 43,300 46.1 2,828 50,800</p><p></p><p>IMR 4831 0.277" 50.6 2,738 44,400 54.0 2,896 50,700</p><p></p><p>Hybrid 100V 0.277" 50.0 2,787 53,600 54.2C 2,964 62,300</p><p></p><p>StaBALL 6.5 0.277" 50.3 2,809 50,200 54.7 3,033 62,300</p></blockquote><p></p>
[QUOTE="Littlehud, post: 2106992, member: 85418"] I know there are some very knowledgeable people on this forum, so I will put this out here. I am a bit confused about some of the load data I am seeing for different powders. Using the same bullet and cartridge, but different powders, I see different velocities and pressures, but not exactly what I expected. As an example, I have the load data for a .270 Winchester for IMR 460 (101), Hodgdon Hybrid 100V (128), Winchester StaBALL 6.5 (129), and IMR 4831 (132) powders. The numbers in parenthesis are the rank number in the burn rate chart. The confusing part is this: H 100V and StaBALL 6.5 have similar burn rates, being #’s 128 and 129 on the chart. They give similar velocities with similar pressures, just as one would suspect. However, 4064 and 4831 also give similar velocities with similar pressures but are far apart on the burn rate chart at #’s 101 and 132 respectively. Why so similar when the burn rate is so different? The other thing that confuses me even more is that looking at maximum loads for the different powders, 100V and 6.5 show 62,300 PSI while 4064 and 4831 both show just under 51,000 PSI. How can there be so much difference for max loads? Why couldn’t you use more powder with 4064 to increase the pressure to 62,000 and get higher velocities? There’s obviously more to the equation here. 270 WINCHESTER Case: Winchester Twist: 1:10.000" Primer: Winchester LR, Large Ri e Barrel Length: 24.000" Trim Length: 2.530" BULLET WEIGHT 140 GR. SFT SP Starting Loads Maximum Loads Powder Bullet Diam. Grs. Vel. (ft/s) PSI Grs. Vel. (ft/s) PSI IMR 4064 0.277" 42.0 2,608 43,300 46.1 2,828 50,800 IMR 4831 0.277" 50.6 2,738 44,400 54.0 2,896 50,700 Hybrid 100V 0.277" 50.0 2,787 53,600 54.2C 2,964 62,300 StaBALL 6.5 0.277" 50.3 2,809 50,200 54.7 3,033 62,300 [/QUOTE]
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