I asked this question in another thread that got a bit sidetracked and never got any takers willing to offer up an opinion.

I am in the process of compiling all the pieces needed to build my first double rifle (not my first "rifle") and have yet to settle on an action. I have been lead to believe that a third fastener is absolutely necessary for these shotgun conversions yet I have seen more than one conversion that had no third fastener and the shooters are still alive to talk about it.

I am not debating the type of third fastener involved, just wether a third fastener is a necessity or a "nice-ity". Say, for a 450 3 1/4" NE or larger cartridge.

Thoughts?