Assuming that the weapons being used are the old FPSC ones and not the newer EWP ones, it is probably worth noting that ammo pools are handled somewhat differently. GG stores ammo pickups in gamecore\ammo whereas FPSC had no dedicated directory and more or less just sort of used the weapon which the ammo pickup referenced.
I am unfamiliar with how Corrosion's scripts work but this could be the source of conflict. As an intermediate solution, you may be able to get away with (in the weapon's gunspec.txt) referencing in poolammo=x one of the stock, known-working ammo types (pistol, rifle, shotgun, etc.) If that works, then it is probably only a matter of needing to segregate/arrange the files in the GG-standard way.
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