I went out today to re-sight my TalonSS in .22 cal. with JSB 18.13 for squirrel hunting. It seems that my shots are averaging further and I know the H&N Terminators I was shooting won't hold their accuracy at further ranges plus less energy too. Anyway to the point of this post. Back in late summer/early fall I chrongraph the JSB 18.13 grain at 750 fps. I decided to check them today and they were only going at 720 fps. I know cold weather affects aspects of powder burning and air guns too. Have any of you guys checked you rifles difference in fps in hot weather vs cold. The 30 fps difference was more than I expected. Bill
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PCPs' Cold Weather & FPS
- Thread starter AirgunBill
- Start date
I have noticed this also. Not shure what the exact reason is, (probably something to do with the density of the compressed air) but I just write down my poi at different temperatures and chart it. I shoot from - 10 f to 90 f .
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Temperature, humidity etc. everything affects your zero. That is why I always check zero right before hunting. The other day I went hunting and noticed that my gun shot about 16 fps slower than the day before, all because of these factors. If you use ballistic apps, you can put the zero temperature and the current temperature in the app and it will tell you how much to correct.
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Could it be the thermal expansion difference between lead pellet and steel barrel?
Looking at linear expansion coefficients (https://en.m.wikipedia.org/wiki/Coefficient_of_thermal_expansion#Coefficient_of_thermal_expansion
) lead has 3x expansion compared to most steels. That means as the system cools, it will be like shooting a pellet with a smaller head size. Simple math suggests up to 0.01 mm size change quite possible at extreme temperature changes (I.e from room to -20 Celsius)
Just a thought, dunno how real this is.
Looking at linear expansion coefficients (https://en.m.wikipedia.org/wiki/Coefficient_of_thermal_expansion#Coefficient_of_thermal_expansion
) lead has 3x expansion compared to most steels. That means as the system cools, it will be like shooting a pellet with a smaller head size. Simple math suggests up to 0.01 mm size change quite possible at extreme temperature changes (I.e from room to -20 Celsius)
Just a thought, dunno how real this is.
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I know there has to be a lot of environmental effects of lower temperature on the components and air pressure. I was just wondering how many people target shooting and hunting take this into affect when shooting from hot to cold conditions. I know when I redid my drop charts particularly at longer distance might make the difference in hitting that old squirrel or other target.Bill
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