Why the heavier #429244 gas check 255 grain bullet load range is 18.2 grains to 22.2 grains of 2400, I have no idea.
I know
exactly why the heavier bullet uses a heavier charge weight - it goes straight back to GB's comment and what I stated above.
The Lyman #47 manual shows this max charge data:
#429421 245 gr - 23.4 grains 2400 - 1232 fps - 36,000 cup
#429244 255 gr - 22.2 grains 2400 - 1165 fps - 35,300 cup
The Lyman #48 manual shows this:
#429421 245 gr - 20.6 grains 2400 - 1248 fps - 37,200 cup
#429244 255 gr - 22.2 grains 2400 - 1165 fps - 35,300 cup
Clearly, Lyman did NOT re-shoot the data for the heavier bullet like they did with the lighter one. Just as clearly, the data for the heavier bullet is now over maximum pressure. Shame on Lyman for this. Modern 2400 is hotter than it used to be.
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