Re: Why still use temp sensitve powders?????
The hot load I found is 57.7 gr Re17 130 gr VLD #27501 moly 3.34" 270Win 22" barrel.
Chronographs 3,228 fps
All 5 cases are stiff force to re prime.
Quickload predicts 3,219 fps 70,604 psi
When I look at Kombayotch's Re17 data, I might get 6.6% velocity variation between -10 F to +170 F.
If I subtract off 6.6% from 3219 fps I get 3020 fps.
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But if I use an extreme powder, 52.3 gr H4895 QL says 3145 fps 70k psi.
If I look at Hodgdon's H4895 data, I might get .6% velocity change between 0 F and +125 F.
If I subtract off .84% [extrapolating to normalize to Kombayothch's temp range] I get 3119 fps
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What does it all mean?
RE17 changes in trajectory [less long range accuracy]
RE17 changes in velocity [ less power]
What does THAT mean?
When I work up a load, and find the max load with long brass life, I have to subtract off that load my own safety margin for variations, to make a useful load.
That safety margin would have to be so large for Re17, that it would wind up being a wimpy load as well as a more variable trajectory useful load.
But with the extreme powder, the safety margin, to reduce below the threshold of long brass life, is smaller, resulting in a more powerful and more stable trajectory useful load.
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What other things contribute to the calculation of safety margin besides powder temperature variations?
*Shot to shot powder charge variation
*case to case volume variation
*Cartridge to cartridge over all length variation
*Bullet to bullet weight variation
*Primer to primer power variation
*Cartridge to cartridge neck tension variation
*Intended use of the ammo from targets to dangerous game