It looks like the ECHO trigger is more stable than the Binary trigger. Sounds cool but not sure if the selector was meant to go to a 3rd position for the S1 model.
The trigger pack housing has a half moon cut and the selector uses a roll pin to dictate it's course of travel. Simply measure the amount of sweep you need, and trim that out of the pack housing. The trick will be modifying the safety drum that spans the pack housing and making it drive a second disconnector. Or, not. And it will have to have some tricky dynamics where the second disconnector falls back to the first if you flip it off of binary function. That's the hard stuff.
If the FCG parts were available at even quasi realistic prices I'd already have one going.
The real trick is probably going to be keying in the FPS arm as a sear trip for added protection of OOB strikes stopping the gun if you get ahead of the lockup.
There is enough clearance between the release of the disconnector hook of the hammer (with a slight reduction in nose profile) and the trigger hooks catching it to allow the hammer to release and near miss the trigger hooks on release. A 30-35 thou shim under the disconnector foot is a good place to start. When shimming to pull out the slop in the FCG you will find this magical zone when you go just a hair too far. Dry runs proved it will ignite on release as the FPS is still depressed enough at this point of travel to allow the firing pin to strike.
I'm unaware of the legality - and what is required to ensure you stay out of the grey areas on this subject so I just let it go. But since it's a dual hook trigger, modifying one disconnector to release so it gets caught, and another hook to not - could give you primary / secondary disconnector function without complicated mechanisms. Getting the secondary to kick down to the primary (SA) disco is the one I can't think my way through. Keep in mind the majority of this subject could be used / misinterpreted for another purpose. But from what I can tell, not reliably, or even remotely safely...
Quite frankly, a binary would be perfect for the little Scorp. They get going plenty good without the retarded bump fire nonsense junking up the gun. I don't think making one for the Scorpion would be remotely difficult to do. But there is absolutely no clarification out there on what keeps it on the right side of the law. What mechanisms it has to have to prevent Ricky Bobby from removing parts and getting himself in trouble. I proposed a group think project - to see if we could engineer it, and then just have one of the major companies doing them to pick it up and make it for us. But, nobody really seemed to bite. Everyone here has this gun and a pair of eyes. The pack housing comes out in 10 seconds...
