I have come onto the possession of a tactical 870 with extended factory tube and fixed choke. It looks like normal barrels won’t fit it. Am I stuck with the setup I have? I would prefer a more versatile shotgun.

any bbl should fit as long as you stick to 3" if it is a 3" gun and same goes if it is a 2 3/4 gun

If it's like this : https://www.remington.com/shotguns/pump-action/model-870/model-870-express-synthetic-ta...

I think you're stuck with that barrel.

Nm