Originally Posted by
BehindBlueI's
The theory behind the design is that under stress people's cyclical rate increases and they start firing unsighted so a mechanical means to slow them down is a good thing. In execution what that means is a long reset and an even longer reset, each with a different weight on the next trigger pull. The theory is this heavier weight slows the trigger pull down and reduces cyclical rate so the panic shooter gets more time to get the gun out of recoil and realigned. Apparently it's better to have panic fire that's a millisecond or two slower, but now with the added benefit of a surprise increase in trigger pull weight, because if it's one thing that's going to increase hit rates it's never quite knowing how your trigger is going to react.
In short, it's the opposite of a DA/SA plus a little slot machine built in for randomness for the people at the training level it was designed to help. Hence it's extreme unpopularity and generally lower desirability on the used market.