It would be hard to line it since the loading rod slides through it. Maybe on the sides there is enough room but then the problem is how to get the material to stick and not move around and get in the way or come out.
I thought of using a barrel band but am not all that familiar with them. It would need a thin one that would conform to the shape of this gun when tightened. I did look around a bit but all I have found so far are thick heavy duty ones that would not do very well if at all, even if they could be reshaped they would not fit unless a lot of modification was done.
The problem seems to me to be that the pin goes into the forend, exits on the side toward the barrel, and then spans an unsupported distance before it goes into the hole drilled through the barrel. Maybe if the pin was supported all the way to the barrel it would not come to mischief. Just a guess, any comments from somebody who knows more about such things? -Ken