I can't speak for the mossberg, but i own 2 870s. My 12 ga i bought last october with the 3 1/2 in chamber. I used it hard all season in the blind. It cycled most shells great, the 3 1/2 in winchester shells jammed the 1st time, but i think that was because when the crimp opened it stuck out a little farther than other 3 1/2 in shells. I had a hard time gettin it to cycle 3 in hevi shot at 1st, but it eventually worked. I don't know if it was just a breaking in issue being a brand new gun. About the 887 i have not shot one but i have shouldered them and i felt like the action wasn't as smooth as my 870.

Hope this helps