If you bought it right, send it off to Briely and have choke tubes fitted, or, better yet, ship it to Tom Wilkinson and ask him to do his magic on it. With tubes you'll possibly end up with nearly 30" barrels, not a bad setup in my view.
If you like short barrels, run a bore gauge and see if there is any choke. Some old timers used to "jug choke" barrels to change the constriction at the choke end. Might just be more work done that you suspect.
More likely a shoulder from when the barrel was originally choke tubed. Just didn't have quite enough room to cut it all out and still have a bit or ramp left to re-install the front sight. The front ramp in the ventilated rib is about gone.
Either a screw in choke got stuck or a bulged or dinged barrel would be to only reasons for hacking them off. Send them back to the seller or offer him a $100.00 and get a refund for the balance. I think he snooked you.