bbbean Posted January 25, 2009 Share Posted January 25, 2009 Its a toasty 20 degrees farenheit today. If I work up a load that makes a PF of 165 today, what should I expect at higher temps? Is there a linear correlation (i.e. X fps per degree F?)? Link to comment Share on other sites More sharing options...
Cy Soto Posted January 25, 2009 Share Posted January 25, 2009 I am not 100% certain but I think that this depends on the brand and model of powder you use. Link to comment Share on other sites More sharing options...
bbbean Posted January 25, 2009 Author Share Posted January 25, 2009 I am not 100% certain but I think that this depends on the brand and model of powder you use. Clays Link to comment Share on other sites More sharing options...
JThompson Posted January 25, 2009 Share Posted January 25, 2009 Most of them hotter is faster.... Link to comment Share on other sites More sharing options...
JThompson Posted January 25, 2009 Share Posted January 25, 2009 This from Howard Smith in and earlier post: "Clays doesn't drop all that much in the cold, but it does get faster as temps go up. The difference from 75 to 90 degrees is a lot more than the difference you will see from 50-65 in my experience. Get that ammo really hot, like in a trunk in the summer, and hang on. Pressures and velocities will go up a good bit. It is still more stable than Titegroup, WST, 231, and a bunch of others." Link to comment Share on other sites More sharing options...
bbbean Posted January 25, 2009 Author Share Posted January 25, 2009 I guess what I'm looking for is a way to guesstimate just how much faster the ammo will run. If I make 165 at 20, shoudl I expect 170 at 80, or should I expect something *much* faster? Link to comment Share on other sites More sharing options...
G-ManBart Posted January 25, 2009 Share Posted January 25, 2009 I guess what I'm looking for is a way to guesstimate just how much faster the ammo will run. If I make 165 at 20, shoudl I expect 170 at 80, or should I expect something *much* faster? The only way you're going to know that is to test it yourself. I wouldn't even be surprised if some individual guns gain more or lose more due to temp change than another otherwise identical gun with the same batch of ammo....you just can never tell until you test. Generally the sample size most of us use for chrono testing isn't large enough to really be certain of the numbers we're seeing. It gets us pretty close, and gives us a reasonably decent average, but that's about it. Using that sort of data to come up with something like X fps per ten degrees increase in temp is likely to give you some pretty unreliable numbers. R, Link to comment Share on other sites More sharing options...
cnote Posted January 25, 2009 Share Posted January 25, 2009 Some powders (WST) are inversely temp sensitive and will get slower with and increase in ambient temperature. Clays is not one of them. This is why it is wise to write the temp on you crono recordings. I have also heard that altitude has an effect also. Link to comment Share on other sites More sharing options...
MichiganShootist Posted January 25, 2009 Share Posted January 25, 2009 I think this is a question that will only be solved with a chrono and not a calulator. Many of the changes are not a mathmatical straight line. Just like bullet over seating.. the further you do it the more the pressure rases and at a continuing faster rate. Link to comment Share on other sites More sharing options...
lynn jones Posted January 26, 2009 Share Posted January 26, 2009 some powders are senitive, but most aren't at all. Link to comment Share on other sites More sharing options...
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