Does the GBBRs' CO2 mags create moisture when shooting at full auto?

[mirrage]

I were talking with a co-player about my intention to buy a GBBR and that I were looking at WE or Inokatsu cause they seem to be good.
I am not yet sure about the value for money relation but I hope to clear this out soon.
During our short conversation he said me that one of the problems with CO2
GBBRs is that when you shoot in full auto the mag freezes and moisture is been creating outside and inside the mag.
Then the moisture enters the barrel and inside all internal parts.
That sounds logical but what I can't know is if the moisture can damage the gun.Aren't they rustproof?


Thank you in advance!