Source?
I have seen many gun shipments over the years. Most are delivered by FED-x to gun stores and by common carrier to warehouses. I have a hard time believing that guns are shipped by rail. It is the slowest least dependable method of shipment.
These were all over the local news at the time they happened:
https://abc7chicago.com/archive/9533218/
https://www.nbcchicago.com/news/local/chicago-train-guns-stolen/149322/