Just found some other info:
This model Cross refernces out to a Remington Sportsman 58, introduced in 1956, the Sportsman-58 was Remington's first gas-operated shotgun. You can request an owners manual for obsolete firearms at www.remington.com
click on sportsmans library, then downloads, then owners manuals, then click obsolete owners manuals, you will have to register but it is worth it to get the free manual.
My buddy has a couple of these and uses them all the time, by the way if you need new barrel he takes a rem 870 barrel and drills a port for the gas-operation. Like on a 1100 or 1187 I would check to see if the gas port is clear, use appropriate size drill bit.