"...it jams or doesn't like to eject..." Sounds like a non-magnum receiver. Too short. Changing the barrel won't help. Especially, considering that if it won't eject 3", it's not going to work with 3.5" either.
Don't see the need or fascination with 3.5" Mag myself. However, "I want one." is a reason. What's your budget? You want a pump or semi?
The Stoeger runs $600 to $750 at Cabela's. $429 for a Mossberg 535 Combo. Comes with a 24" deer barrel. $600ish for a 935. The 935 is a 3.5" semi-auto. A Browning A5 runs $1549. An 870 Express Super-Mag runs $379.99.
There's a bunch more in assorted price ranges.
https://www.cabelas.com/category/Mag.../571842180.uts