Buzz:
As Rabbit mentions, not ALL Superposed double triggers worked both barrels. I own one of the very first Lightnings with double triggers. They are simply plain double triggers with no interconnection to both barrels. This is just the way I like them. Quick, positive and foolproof. Unfortunately, I cannot say the same about Val Browning's inertia trigger, which I consider only 90% reliable. Especially with lighter loads.

Best, Kensal