That is unfortunate about the 600 breaking.

Personally I do not understand why anyone would use the rear trigger of a double first. It is counter-intuitive and invites screw-ups under pressure. Further, it partially defeats the elegant design of a double trigger system which allows the rapid firing of a 2nd shot.

If I cannot handle my double in the FRONT-TRIGGER then REAR-TRIGGER sequence, then I need more practice. However, using the front then rear order, I have had no doubling (accidental or otherwise).