Gentlemen:
Thank you for your answers.
Juan Carlos: I have the time and patience to slowly modify some shotshells and made spreader loads with a plastic post in the center of the pellet charge. With those spreaders I "open" the choke from full to mod in my P. Arrizabalaga 20ga left barrel.
The Beretta shotgun in question is not mine and belongs to a friend that prefers a permanent change in the chokes.
Two Georges: Both comments very usefull. The special reamer to cut chrome is, as I know very expensive. I will learn more about the automotive device to hone with stones and decide if is a posible option.
Any other advise to my question?
Best,
