I'm looking a fine Dougall 16 bore double rifle with the lockfast action. The gun is in very good condition for it's vintage, but I can detect a slight amount of play indicating that it is off the face.

Given the eccentric cam-action in this mechanism, I would speculate that perhaps there is some adjustment that can be made, rather than using traditional methods employed to put other doubles back on face.

Does anyone have any expertise regarding this?

Also, any comments on the merits of the polygonal rifling found in this gun?

Cheers!