Temperature sensitivity doesn't turn out to be all it's cracked up to be.
This article is interesting.
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Originally Posted by Slamfire
Such small numbers are well within the manufacturing technology of powders. Then the different lots are blended.
Accurate Arms told me they blend powders to 5%, (pressure curve I think), and that was half of industry standards.
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Actually, its burning rate they blend to, so you can see why the order of powders on different burning rate charts aren't always the same. It depends what lots were measured for the chart. A lot of spherical propellants can vary 10%. I believe a Hodgdon tech said their stick powder lots are blended within 3% of standard (meaning the Extreme line of powders). Performance in the gun, however, doesn't depend just on burning rate. Indeed, burning rate changes with pressure and can change order among powders at pressures different from the one at which burn rate was measured in the caloric bomb. So it's messy. Knocking down 10% and working up is about the only option if you don't have a Pressure Trace to get a matching pressure reading with.
TXGunNut,
When Hodgdon acquired IMR and took over marketing for Winchester powders, it looks to me like they incorporated a lot of the load data already developed by those two brands into their data. Apparently IMR never developed any data for 7.7×58, so it doesn't appear in the Hodgdon load data, either. Even the Hodgdon data listed has no corresponding pressure listing, so I don't think they own a pressure test barrel for it. If they no longer have the rifle they used to work up the original Hodgdon data, they may never work up any IMR data for it.