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FPS SPEEDS AFFECTED! !!

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Sure. There is a Pressure, Volume, Temperature relationship (Ideal gas law PV=nRT) that will be directly impacted by the temperature of the air. Cold air in your pcp will lower the pressure with the same volume. Also the air that the pellet is traveling thru will be denser when colder, thus slowing down your pellet and having an effect on Point of Impact. So in a nut shell "Yes", cold and warm weather will play havoc for us airgunners.
 
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I always find it interesting updating the weather on Strelok pro and seeing how much the vertical correction is from the previous settings. This would only be external changes though not the air in my gun. 
I use this app a lot and works very well. 
Does a charge of cold air versus a charge of warm air make a difference if the pressure of both is the same?
 
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"Grin_Reaver"FPS is affected and is most troubling when it happens in a single day when you go out early morning and keep shooting until the sun makes it much hotter.
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This is of particular interest to me ( I usually set up in the morning and will shoot sporadically throughout the day, mostly pesting). Does this always affect all PCPs regardless of make or kind? What about say an FX Streamline with it's Regulator vs say a Regal XL without a regulator? I had always heard how temps affected CO2 guns, but I thought PCPs were fairly immune to this. Does temp changes affect Springers?
 
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"AirSupply"I agree speeds vary depending on temperature but the pressure should only vary in the bottle. The regulator will still do its job and give you the same pressure for each shot regardless of the temperature of the air.
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I agree that the reg will help with that. One thing to consider is that the colder more dense air does make a difference in how it expands. So colder air at the same volume will expand slower. that might be enough to change the amount of "energy" imparted from the same size charge provided by the reg. All kinds of crazy complicated calculations are involved to prove that. :)
I just notice then when my gun is cold, not only does the fps decrease slightly, but I also use a bit more pressure per shot therefore giving me few shots on the same tank. Pretty normal stuff. Ain't science a wonderful thang?

Crusher
 
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Don't forget that a scope, more so those on the cheaper side of the scale will shift a great deal as well. It might go a bit blurry for it's set parallax, or range a bit short if using the AO for multiple ranges.

Also don't forget the springs in your guns as well. Both PCP and Springer. Colder than normal(whatever normal is for you) will stiffen your hammer and valve return springs. Dissimilar metals like a steel air tube threaded into an aluminum valve housing to tightly will bind when too hot or cold thus causing a poi shift.

Those who like to grease/tar the bejesus out of their mainspring and tube will notice a drop in speed when colder, and an increase in speed when warmer. Also if there is too much lube and things get hot, and the gun(springer) is left in the sun to cook for a bit lube can migrate past the piston seal and give ya bit of a suprise with the next round.

I will say that it takes a smaller temp shift/range to effect the velocity of a springer vs a pcp but they do both do it. Altitude has a noticeable effect on springers as well though it's a matter of a thousand feet or more above or below your everyday shooting elevation before you will notice a difference.

All of these observations have come from filed target shoots that have us starting the day at 40f or less and finishing at 65f+ in the spring and fall while the guns may be resting in the sun or out of it during the match. If you don't catch the shift or know how to correct for it things can get rough(not fun) quick.
 
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Knowing these shift occur there are a few ways to map them. Most shooter have an aquarium or similar temp strip on the scope or part of the gun/stock. Either during matches or during practice you pay attention to when your poi shifts. When it does you look at the temp, tube pressure and if you can a chrony(when home) test to eliminate as many possible reasons for the shift. Once you've determined that it's the scope, gun or you then take note of were the shift moves things and at what temp it moves. Most of the time it's the scope, even the expensive ones that will move a bit, not so much your guns speed. As for correction during a match you can adjust your clicks, or hold off a bit(kentucky windage) to correct for it.
 
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