I should clarify, I wasn't saying they dropped in a trigger system.
the thread on Ar15.com (43 pages) shows multiple videos of people shooting faster on stock triggers that came in the guns they bought factory new.
The Taccon trigger has a "quick reset" which allows the user to increase the ROF.
here is a stock DDm4v5 trigger
http://www.youtube.com/watch?v=GBO2DrgbSMM
here is the 3mr, go to 1:15 (fastest shooting).
http://www.youtube.com/watch?v=ZnDoQtSH7NM
Why would someone need a 3MR?