Darne R-series hands down, and probably the most durable as well. I've seen many loose Webleys, screw grips and all, and I've also seen a couple of loose Manufrance Ideals. I have NEVER seen or even heard of a loose Darne or a Darne with blown barrels or damaged action. Only problem I've heard of regarding Darnes are the stocks.

Guns built using the Jones Underlever system would probably be next in line. I'm not talking about underlevers with a spring that "snap" back automatically, I'm strictly refering to the manual lever system that actually "SCREWS" the barrels down to the action.