Jose,
It's a slow process, but you can cut through the chrome at the chokes with an automotive wheel cylinder hone and cutting oil. You may have to change the stones in the hone several times before all of the chrome is ground away. I've successfully done this job on chromed barrels on a Garbi. The pattern placement was not affected. After the chrome is removed, then use your reamer to open the chokes to the desired 0.005 and 0.010. Take your time.
George