What is the best method for opening chokes in chrome lined shotgun barrels?

The same as you do with normal unlined barrels. Using a variable choke boring tool.

being that most hss reamers won't cut chrome your choice is a carbide reamer or hone out the chrome. it is pretty easy to tell when it is gone. just touch the metal with cold blue. if it colors, the chrome is gone.

Thanks I guess I won't use my remers as they are not carbide again thanks for the reply.

Clymer once made an expanding carbide tipped reamer. They don't sell this any longer but at one time 4-D had one for rent and probably still does. This tool was made more for removing the chromed choke section prior to tube installation. You'll still want to hone and polish the bore to size after using the tool.

4-D Reamer Rentals http://www.4-dproducts.com/display.php?group=Shotgun