I wouldn't do it, contact Briley or Kolar, sub Gauge steel chambers/choke tubes with Aluminum shafts not designed for steel shot.

 

Good advice.

 

FYI - from Briley:
“You can shoot “gun club” steel out or the tubes, just no magnum loads. The 20ga also need to have extensions between the chamber and aluminum as well as a hard coat anodizing. If you are sending us a gun/barrel for ta new tube set, please specify you will be shooting steel shot.”