I have one tube fed semi-auto shotgun - a 12ga Rem 1100 magnum with 30" barrel. It was after I bought it that I learned how, in my opinion, peculiar a shotgun it is.
I'm talking about the feeding-cycling system. Where the bolt is locked back after each shot and is released by a tab hit by each shell as it feeds from the magazine. I have an extended 10rd tube on mine and it has fed perfectly, but I can tell very clearly that the cyclic rate is changing.
I'd almost say "to heck with the 1100" and go with another tube fed semi, but then I'd have to ask if any or most other tube fed semi-autos work that way?