I have a 30" Remington 870 barrel that is chambered for both 2 3/4" and 3" shells. It is threaded for Rem Choke tubes and I'll include a flush Mod choke with the barrel.
The rib is about 0.290" to 0.300" wide and has a white front bead and a silver center bead. It does NOT have a step rib. The barrel is a bright polished blue finish and it came off my Wingmaster shotgun.
I bought the gun lightly used about 10 years ago and probably haven't put over 250 shells through the gun since then.
If you want the barrel, I'll take $220 shipped to you.