I was recently down in Texas in 90 degree weather, and doing some shooting on our deer camp shooting range there.
I had loaded 5 powders to compare in my .338 Lapua Magnum.
N560
N565
RL-26
Retumbo
H1000
Previously I have had velocities for 84.9 gr N560 in the 2825-2850 range for 250 gr Lapua Scenar bullets with this rifle using Lapua Brass. It has a 26 inch barrel. The first 3 warm up rounds I shot, average 2916 fps from a cold barrel.......that shoulda been my first clue, something was up.
I shot some RL-26 rounds loaded with 90 and 90.1 Gr RL-26 using same 250 Gr Lapua Scenat bullets. They averaged 2979, and 2998 fps respectively.
I was expecting something more like 2870 out of these rounds based on QL and burn rate of .3397 for RL-26.
I had some 86.4 gr rounds N560 that then averaged 2931 fps, and then I shot 3 rounds of N560 at 86.9 gr that averaged 2944.
Based on previous work with these and modeling in QL I was expecting 2870 to 2885 fps at a burn rate of .3873
In reality, when I tried to figure out the actual burn rate for N560 it was in excess of .405 indicating temperature in the chamber had to be at least in
the 120-130 degree range. The RL-26 velocities were off the charts hot, and there was no way to make QL even go above 122 F to see what the actual burn rates were. They were certainly a lot hotter than .38 which is way hot for RL-26.
Since then, I have done some research on temperature sensitivity for these powders. It appears they were probably the most temperature sensitive of the powders (at least in high temps) I had loaded that day. I did not get to shoot any of the Retumbo, H1000, or N565 loads because I had a case head separation on the last N560 round that measured 2945 fps with 86.9 gr N560.
From what I have read, N560 is not as temperature insensitive as N565 and N570. It seems to have more sensitivity than the other V V's listed.
I read some horrible accounts of RL-26 at high temps with near max loads. It goes ape**** and bat**** at near max loads in hot weather.
It is supposed to be somewhat temperature insensitive, but over 90 degrees, that may be a myth based on my experience.
I see a lot of these temperature tests are run by freezing loads, and then testing them against room temperature loads. My take is this is no way to
state whether these powders are temperature insensitive. It covers only one tail of the distribution. Of course, I don't expect anyone to put their loads in a microwave and heat them up, but maybe taking them into 90 degree temps and shooting 15-20 rounds tells you something like it did me.
I think the Swiss, and the Fins, have no idea on the powders they manufacture what temperature sensitivity really is when they have never
experienced an August in Texas or Arizona. This is making me lean towards the Hodgdon's extreme powders or the Enduron Extreme powders for
shooting in really hot climates. If you have similar experience by all means contribute. Going from shooting in Michigan to Texas is a learning experience.
I had loaded 5 powders to compare in my .338 Lapua Magnum.
N560
N565
RL-26
Retumbo
H1000
Previously I have had velocities for 84.9 gr N560 in the 2825-2850 range for 250 gr Lapua Scenar bullets with this rifle using Lapua Brass. It has a 26 inch barrel. The first 3 warm up rounds I shot, average 2916 fps from a cold barrel.......that shoulda been my first clue, something was up.
I shot some RL-26 rounds loaded with 90 and 90.1 Gr RL-26 using same 250 Gr Lapua Scenat bullets. They averaged 2979, and 2998 fps respectively.
I was expecting something more like 2870 out of these rounds based on QL and burn rate of .3397 for RL-26.
I had some 86.4 gr rounds N560 that then averaged 2931 fps, and then I shot 3 rounds of N560 at 86.9 gr that averaged 2944.
Based on previous work with these and modeling in QL I was expecting 2870 to 2885 fps at a burn rate of .3873
In reality, when I tried to figure out the actual burn rate for N560 it was in excess of .405 indicating temperature in the chamber had to be at least in
the 120-130 degree range. The RL-26 velocities were off the charts hot, and there was no way to make QL even go above 122 F to see what the actual burn rates were. They were certainly a lot hotter than .38 which is way hot for RL-26.
Since then, I have done some research on temperature sensitivity for these powders. It appears they were probably the most temperature sensitive of the powders (at least in high temps) I had loaded that day. I did not get to shoot any of the Retumbo, H1000, or N565 loads because I had a case head separation on the last N560 round that measured 2945 fps with 86.9 gr N560.
From what I have read, N560 is not as temperature insensitive as N565 and N570. It seems to have more sensitivity than the other V V's listed.
I read some horrible accounts of RL-26 at high temps with near max loads. It goes ape**** and bat**** at near max loads in hot weather.
It is supposed to be somewhat temperature insensitive, but over 90 degrees, that may be a myth based on my experience.
I see a lot of these temperature tests are run by freezing loads, and then testing them against room temperature loads. My take is this is no way to
state whether these powders are temperature insensitive. It covers only one tail of the distribution. Of course, I don't expect anyone to put their loads in a microwave and heat them up, but maybe taking them into 90 degree temps and shooting 15-20 rounds tells you something like it did me.
I think the Swiss, and the Fins, have no idea on the powders they manufacture what temperature sensitivity really is when they have never
experienced an August in Texas or Arizona. This is making me lean towards the Hodgdon's extreme powders or the Enduron Extreme powders for
shooting in really hot climates. If you have similar experience by all means contribute. Going from shooting in Michigan to Texas is a learning experience.
