There are over 110 barrels for the 12ga 870. Yes, many are the same barrel but in different finishes but this still makes this the most versatile pump shotgun made. Just to compare, there are only 11 made for the Mossberg 500. For the barrels below make sure you understand the finishes. Matte finish is the finish for the Express shotgun and is an applied finish made to look like Parkerizing. Special Purpose finish is the same matte finish, however they polish the barrel more to make the finish look smoother. Blued is the finish of the Wingmaster. Marine is a Nickel finish. There is a Poly Coat Finish that is matte Black and never needs Oiled. It is a decent coating and the flaking issue of years ago was resolved when they found the guy skipping a step in the application process and fired him. I have had a couple guys complain about the Parkerize barrels having the gold bead between the barrel and sight base and also the stand off block. This is the brazing and because it has nickel in the composition it will not take Parkerizing. In fact that is how I can look at a matte finished Express 18.5" Bead sight barrel from a distance and tell it is an Express barrel. If I don't see that gold bead under the sight I know it is an Express barrel. One guy was so anal he wanted to return the barrel to me and have me paint that bead black. I of course said no but Offered a refund. I guess he painted it and is a happy "Tacti-fool" gun owner now.
Most Express barrels do not have the barrel ring detent plunger that retains the magazine cap or mag tube coupling. If you are going to put this barrel on a Wingmaster or Police you simply get a "Wave Washer" This works great, so great in fact that Wilson Combat include then for their Tube Extension when installing on an Express Barreled shotgun.
Cyl - Cylinder Choke, Also called Cylinder Bore, is the most open choke with little to no restriction at the muzzle
IC - Improved Cylinder is more restriction then Cyl and the best all around choke for a fighting gun
Modified - Is more restriction the IC and provides tighter patterns, however does do well with Flight Control ammo
Full - Is generally he most restrictive choke and not available in short 870 barrels, is mostly a sporting choke
RC - Stands for Remington Choke, also called Rem Choke, these are threaded insert changeable choke tubes
BS - Stands for Bead Sight
RS - Stands for Rifle Sights
Trit - Stands for Tritium which is a glowing liquid use in gun sights.
GR - Stands for a Tacti-Fool mess that has no place on a fighting shotgun, also Called Ghost Rings
Hi-viz - Stands for High Visibility, can be simply a bright white sight or some kind of fiber optic
VT- Stands for Vent Rib, this is a raised rib that runs along the top of the barrel and the Bead sight is on the end.
MT - stands for Matte finish, with Remington that is the Express Finish
WM - Stands for Wingmaster, these barrels are a high luster blued finish same as the Wingmaster receivers.
PK - Stands for Parkerized. Only the 870 Police and the 11-87 Police Barrels are factory Parkerized.