Yes sir they surely do or have made them. Multiple .410 models with the 18.5. Now, where is just a barrel 18.5 to purchase ???????? Some google searchin has almost led me to believe just buying a used .410 barrel on fleabay for 50bucs and cutting it to size would be my method to solve the riddleDoes Mossberg make a a 18.5" cyl. bore barrel for a 500 in .410 gauge?
Same result as you looks like them .410 barrels are scarce. Maybe a pawn shop journey find a barrel with a complete spare parts kit attached alreadyLooked on ebay, want more than buying complete. Plenty of 12 and 20"s, no 410 reasonable.