Remington 870 barrel swap

[rapier144]

My nephew has new 16ga 870 and wants to put on a 20ga barrel can he do that without any problems. Will it hurt anything to do this?

[VaultDweller]

The reciever, magazine tube, and many internal parts in an 870 are designed for a specific diameter and chamber pressure of a given gauge.

It just won't work, the barrel won't even fit on the reciever.