FX Impact M3 sweating

I recently bought a FX Impact M3 and have been experiencing what I call sweating around the rear of the barrel and onto the plenum. I was told by the dealer and FX that it may be humidity, warm weather causing it. I am not seeing any reg creep or fill pressure loss? Has anyone else experienced this?



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I was going to say it's the plenum cooling with the pressure drop after every shot and causing the condensation on the rear of the plenum when it cools below the dew point in a humid environment, but the patch of condensation on the upper frame hints that it's possibly an air leak from the breech area.

Drape a small piece of light tissue paper or toilet paper over the cheek rest and breech area where the condensation is happening and take a shot and see if there's an air leak. Make sure you're firing a pellet so there's plenty of pressure in the barrel. If the paper jumps, there's a leak.

It's possibly a transfer port or breech liner lock o ring leak that's leaking air near the rear of the plenum on every shot, and that blast of rapidly expanding and cooling air is what is causing the condensation. Hopefully it's not any o rings in the valve or rear block, that's a more involved repair.
 
Like I mentioned earlier, it could just be condensation forming because the plenum and breech area are cooling below the dew point from the air expanding in the transfer port and barrel on every shot, or it might be an air leak after the valve seat near the breech area. The simple tissue paper test will let you know.

If the tissue paper test shows there's no air leak from the breech area on each shot then there's nothing wrong with the rifle-- it's just condensation forming on the parts of the rifle that are at or below the dew point for the current conditions. The more shots you take in quick succession, the cooler those areas will get. 

It's just somewhat odd to me that your picture shows condensation on the outer barrel shroud and the upper frame, which is why I suggested checking for an air leak near the breech. Hopefully there aren't any leaks.

Report back with what you find!