What is that 3rd fastener? I don't think I've seen that before?
Looks like overkill -- but that looks like a huge rifle.
OWD
This article below shows the Westley Richards (WR) dolls head third fastner photo at top left. Also shown is the Rigby rising bolt third fastner and the author calls it the best and most difficult to build. The WR is more difficult to build than the Rigby and you can see that when you view the photo of the WR dolls head and see that it is curved and that the curved surface area has to fit into the action in a zero clearance fit--which raises the question how can the fitting of the WR curved dolls head be accomplished to where it fits perfectly while at the same time the bolt fits perfectly into the rear lump of the barrels---the answer is that the action maker has life long experience.
https://www.riflemagazine.com/double-gun-bolting-systems
