I was just thinking about this under the barrel are the tabs that lock the barrel into place one of my barrels (I'm messing with it right now) was tight to open I had to really jam on it to open when I first bought/installed it.
So I took my dremel and lightly ground down on the lip of the lock tabs until the barrel started to open without to much force it is still a bit tight but snaps open readily now.
Sorry I didn't mention this before Dwayner I had completely forgotten about it.
and welcome to Greybeards...