I believe that you can open the chamber to 12 gauge. I have one that was thus treated and it shoots like a card shooter.
I understand what you're suggesting but wouldn't shooting a 12 ga load down a 14 ga barrel significantly increase the pressure?
Perhaps someone who has done this conversion will comment here. I am reluctant to suggest this to a friend without insurances that the resultant gun will be safe.
If the green light is given does anyone have a recommendation of someone who would perform this conversion?
Jim