Yes, Bryan is the man! Now that you have provided the actual altitude, what do you get using your AB for the information below?
Load development environment: 675' at 80°F
Vs.
Hunting environment: 8000' at 50°F
Magpro Powder
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Load development environment: 675' at 80°F
Vs.
Hunting environment: 8000' at 50°F
SSG Graybush
Well-Known Member
For H1000 at listed altitudes and temps, 50% RH, 10 mph FV wind. 7mag- 2917 fps 180 gr vld-h. I have .31 fps per degree in AB for H1000. As for spot on in WY, 2 shots on a 18" rock, pretty centered ~ 4" apart, I was getting blown around, cold bore and follow up at 475 yards/25 mph FV wind.
So for RL 26 and Magpro it would be triple the variance at 1.01 fps per degree. If Magpro is 1.01 fps per degree as I've seen online. I've seen 1 fps per degree with RL26.
In WY I get an average temp for upcoming days and do 1 dope card and tape to scope. With H1000 it's close enough, but with a temp sensitive powder it's not possible. You'd have to run #'s real time for AB to compensate for fps variance due to powder temp sensitivity/change in fps.
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According to your table, if I understand correctly, at 1000Y, it is a velocity gain (not lost) of 201 FPS transitioning from 675' elevation at 80°F to 8000' at 50°F. So, yes, you must adjust to the changing real-time environmental information to acquire your best dope.
SSG Graybush
Well-Known Member
Yes it's always better to have exact conditions for best dope output. But dont mix attitude adjusment/verification with velocity changes due to powder sensitivity. You must verify your ballistic data at altitude to ensure your app is adjusting properly for the thinner air at 8000'. But once confirmed with a temp stable powder you can average the temps of your hunting days and make 1 dope card for that attitude. Say 20 to 60 degrees is the temp swing in your hunting area(like WY), using 40 degrees will get you close enough with a temp stable powder. Being off ~6.7 fps max with H1000, compared to ~20 fps max with Magpro or RL26.
I am not confused between altitude and velocity, as well as the effect of altitude on velocity. I was trying to rationalize the 30 FPS loss from 80-50°F you initially noted. I think you're missing my point. What do you do with the difference in FPS, regardless of whether it is ~6.7 FPS with the H1000 or ~20 FPS with Magpro or RL26? That's the adjustment I was referring to—the adjustment after you make the environmental adjustments at base X. What is the drop at distance X you need to adjust whether the loss in FPS is 6.7 or 20 FPS. This situation does not cause me to panic.
Bryan Litz did not say not to use double-base powder but to know your environmental conditions and how to adjust them accordingly. In his example at the 2:20 minute mark, if you developed a max load with double-base powder in Michigan in winter and compete at Phoenix in summer, you might not be able to finish because of the extreme temperature difference, especially when it is already a max load, because you did not allow for the difference. This would be a severe panic situation. However, it is not all the powder's fault. The nut behind the shooter is the most significant factor. I used to live in Tucson, AZ, in the early 1990s and have real-world experience with the freaking heat. I do not miss it one bit. My son is stationed there now.
I have been using RL-17 for over a decade, another noted powder that is supposed to be temperature sensitive. However, I have learned to adapt to the 30°F temperature swing without any issues. Yes, I have plenty of temp-stable powders, too.
Cheers!
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