No problem exchanging an 870 Express with an 870 Wingmaster. As mentioned before, the only difference being the finish - matte vs blued. I have done this with several different guns after consulting a gunsmith. The barrels are identical. As a rule though, and like it was already stated, when choosing the length of shells to use, you have to match the shells to the barrel first, then match to the receiver. In other words, a 2 3/4 " barrel on a 3" receiver will still only handle 2 3/4" shells. Similarly, a 3" barrel on a 2 3/4" receiver, will only handle 2 3/4 " shells. You always have to use the smallest shells that the barrel and receiver have in common.