I test fired it last night. It's about 2and a half to 3 inches in length. We won't talk accuracy...this one is for up-close and personal protection.
Well, I see they have issued an ammunition advisery with it. Double-discharge is something I'll have to check out before firing it again.
I like it.
How's the hammer cocking force on it? My understanding is that many derringers require sufficient cocking force that single-handed operation is difficult. I wouldn't see why the mini-revolver would be any different in that regard.
One thing I've thought might be interesting would be a two-barrel derringer with three mainsprings and three cocking mechanisms. One (called "A") would be tied directly to the hammer, but the other two ("B" and "C") would be capable of driving it as well.
Prior to use, springs B and C would be cocked, while spring A and the hammer would be decocked. Pulling back on the hammer all the way would cock it and connect spring B. Pulling the trigger would then cause both springs A and B to drive the hammer. At that point, spring B would disconnect; recocking would connect spring C, and pulling the trigger would cause the hammer to be driven with springs A and C.
In this way, the force required to cock the hammer in a 'crunch' situation would be minimized (spring "A" tension would be set so as to avoid having the hammer get cocked accidentally; springs "B" and "C" would be responsible for most of the firing energy). The mechanism would be a little complicated, but not necessarily much worse than a double shotgun.