Look like Bradley's. If that is the case, the barrel of the vehicle (25mm) is always removed for transport.
No sense giving birds a chance to nest in them I suppose.
It may be an innocent exercise but the fire power is quite impressive. Thinking as well that is has a global presence.
There are other reasons as well. But what it boils down to is that the gun system is simply to valuable to expose to the elements unnecessarily.
Most Americans must really have no idea to the actual power of their military.
That one train will hold more armour than some countries
That's about a brigade's worth of IFVs right there. Not really a whole lot, considering there are probably other vehicles like tanks, recce vehicles, Humvees, and various support vehicles all coming in on other trains. It might seem like a lot, but really, it isn't.