If I were you I would look for a barrel that is the length you want that has some sort of choke, or interchangable chokes. If you cut it down it will have no choke. I have found that even up close a tighter choke is better. I did a test with some medium density fiber board (3/4 inch). The tighter choke had more penitration with game loads.

I also wouldn't suggest cutting the barrel down to an illegal length either. Could just be more problems for you if you had to actually use it.

Paul