They make a 410/45 Colt barrel. You can check out the other barrels on hr1871.com under the barrel accessory program.
The 410/45 Colt barrel is rifled. My understanding is that for the 45 you leave the choke out, and for shot from the 410 you use the choke to stop the spin. Accuracy reports for the 45 are poor. You can search the forum at hr1871.com for more specifics.
Neal