I recently went through this decision and bought the 20 ga with a 28" barrel. Started with the 20 ga because I felt more comfortable with my wife learning to use it. I liked the long barrel because we also want to start sporting clays. PHX has a great program to start women out with clays. Anyway, on to my question.
I was told that an 18.5 - 20" barrel would be no problem to find. I find all kinds of options for the 12 ga. Why am I having so much trouble finding a HD barrel for the 870 20 ga?