Temperature
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tahunua001
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air molecules move more when hot than cold. you also have to account for how thick the air is to begin with. if your shooting range varies greatly in feet above sea level then that can affect your ballastics way more than 20 degree temp difference.
Example for 40° vs 20°,
When using a .22 lr, a subsonic round could become a supersonic round if its cold enough.
The speed of sound is slower in the cold, so maybe that subsonic .22 lr at 1000fps can now break the sound barrier.
This would change trajectory I imagine... Have not tried this theory out, but kind of a fun fact I picked up a while ago.
When using a .22 lr, a subsonic round could become a supersonic round if its cold enough.
The speed of sound is slower in the cold, so maybe that subsonic .22 lr at 1000fps can now break the sound barrier.
This would change trajectory I imagine... Have not tried this theory out, but kind of a fun fact I picked up a while ago.
Corrected data to match Hatcher's Notebook info
Cold powder shoots bullets out slower than hot powder. Some tests were done with the .30-06 showing for a 1 degree change in powder temperature, there's about 1 to 2 fps change in muzzle velocity. Details can be seen at:
http://books.google.ca/books?id=yES...&q=muzzle velocity powder temperature&f=false
At long range with the .30-06, there's about 1.5 to 2 MOA change in elevation on the sight for every 50 fps change in muzzle velocity. At 100 yards, the change is about 1/10th MOA.
Cold powder shoots bullets out slower than hot powder. Some tests were done with the .30-06 showing for a 1 degree change in powder temperature, there's about 1 to 2 fps change in muzzle velocity. Details can be seen at:
http://books.google.ca/books?id=yES...&q=muzzle velocity powder temperature&f=false
At long range with the .30-06, there's about 1.5 to 2 MOA change in elevation on the sight for every 50 fps change in muzzle velocity. At 100 yards, the change is about 1/10th MOA.
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I won't argue with Bart, but the numbers I've seen are closer to 1 fps for each 1 degree temperature change with MOST powders. It is possible we are both right and it depends on the individual powder tested. There are powders that are formulated to be more resistant to temperature changes. They still are affected, just by a considerable less margin.
Unless you are talking about EXTREME changes it is not a huge factor for most people. If a load is developed @ 70 degrees it will be about 50 fps slower at 20 degrees. For most people, at common hunting ranges that is not a huge factor. But at EXTREME ranges, or even greater temperature changes it could make a difference.
It goes both ways. As a handloader a load I develop in the winter at 30 degrees could be safe in January, but a hot overload in August at 100+ degrees.
Unless you are talking about EXTREME changes it is not a huge factor for most people. If a load is developed @ 70 degrees it will be about 50 fps slower at 20 degrees. For most people, at common hunting ranges that is not a huge factor. But at EXTREME ranges, or even greater temperature changes it could make a difference.
It goes both ways. As a handloader a load I develop in the winter at 30 degrees could be safe in January, but a hot overload in August at 100+ degrees.
ndking1126
New member
jbmballistics.com has a great calculator you can change temperature, humidity, elevation and other stuff for your specific bullet weight and muzzle velocity.
It would have to get down to minus 44 degrees F to make a 1000 fps bullet supersonic.
1070 fps standard velocity is supersonic when you get down to the teens. I was shooting some Remington Sub Sonics on a really cold winter day and occasionally I would hear a supersonic crack.