If the Wingmaster came with a "Light Contour" barrel, I believe you will more than likely need a forend with a larger "Barrel Groove" or some sandpaper to make it fit.
As to Tom's point about the ball detent vs. the internal ratcheting dealio, I think that has to do with the vintage of the gun - Didn't they switch all the 870s, 1100s, and 1187s over to the ratcheting thing?
At any rate, the (newer vintage) 870 express barrel that I bought for my (older vintage) Wingmaster had a hole for the detent, so I bought the parts and installed them. I actually used the express barrel for a year or two w/o the detent and it wasn't a big deal as long as I kept an eye on the tightness of the magazine cap.
Another thing I had to do with the (cheap crap) Express barrel was polish the chamber so my (cheap crap) Federal Blue Box steel shot would eject after firing. Common problem with expresses I found out.
Good luck!