Can somebody tell me what is the visual diference between a M4A1 with dry ammo storage and one with wet ammo starage. I´ve search in the known places with photographs in the web but I´m confused because I think there are some errors about this matter.

The main thing I look for is the style of hull hatches. The dry stowage M4A1s have the narrow hatches and extended hull housings for the direct vision blocks, even after they were deleted. The wet storage M4A1s usually had the large diagonally mounted hull hatches like those found on later M4A3s. One other thing to look for is applique armor on the sides of the hull. The late model dry stowage M4A1 hulls with larger hatches almost always had extra armor added, whereas the wet stowage late M4A1 did not.
I hope this helps a little!

It also appears that the late, large-hatch hull had more variations. The dry stowage types usually had applique armor as noted, but some hull castings had the molds scooped out to provide thicker armor where applique was fitted. This looks like the latter but with very smooth contours blending into the rest of the hull shape except at the very bottom edge wehre there was a sharp edge just above the sand shield rail. My own suspicion is that this arrangement was the final one, and probably was used with both wet and dry stowage tanks. Even though the wet-stowage tanks wouldn't "need" the extra armor in these places, the ammunition having moved to the lower hull, I can't imagine reverting to a lesser armor basis. Crews would freak out; more armor is always better from their point of view.

Greg

Thanks War_Machine & Greg. Your responses are very clear.