The Knights two-stage trigger was developed by Eugene Stoner while he was working with Knight's Armament. As part of this development
developed a superior two stage trigger for the AR-15, SR-15, SR-25, and AR-10.
Knights Manufacturing Description of the 2-stage trigger:
The KAC two-stage trigger groups offer a substantial enhancement of semi-automatic accuracy potential over factory single-stage triggers for AR-15 Series rifles.
The factory single stage trigger mechanism releases the hammer (firing the weapon) after a steady squeeze is applied by the trigger finger. This trigger squeeze requires steadily increasing pressure to overcome the sear spring and mechanical resistance. The "creep" inherent in the factory single stage trigger requires that the shooter take time to "walk" through the trigger pull and find the "let-off point" in order to achieve accurate fire. In the semi automatic mode the KAC two-stage trigger mechanism release the hammer (firing the weapon) after two distinct amounts of spring and mechanical resistance are overcome by the trigger finger. The Initial stage of resistance encountered with this design feels light and is relatively long - approximately I/8 of an inch. The second stage of resistance feels noticeably greater but is of very short duration. The result is an extremely predictable, consistent, "crisp" trigger pull; semi-automatic fire is both quicker and more accurate because the first stage is quickly overcome and the second stage is crisp and predictable.
This is truly a "drop in" trigger, requiring very little adjustment, It is available with two disconnector springs- One spring (the red one) sets the trigger up to be a 3 1/2 pound trigger suitable for Match Rifle usage. The other spring (the blue one) set it up to be a very crisp 4 1/2 pound trigger.
Most Highpower shooter who have used this trigger say it is the best feeling trigger they have every used and it is also the easiest for the average shooter to install and adjust. And if need be it can be changed to be a Match Trigger. Note the pin holding the two part disconnector in the trigger body. This is the key to the easy installation. This whole assembly (trigger with two par disconnector pinned in place) is dropped into the lower, and the normal trigger pin previously removed is re-inserted. The normal pin pushes the Stoner half pin out and your are done! (well you do have to put the hammer in, maybe 30 more seconds... tops!) This trigger normally needs no further adjustment. You can tweak the Allen screw shown near the front of the trigger if you want to adjust the creep on the second stage. Normally they come pre adjusted. The trigger is available in either a 4 1/2lb or 3 1/2 lb. version. The weight is changes by changing the disconnector spring. If requested, both springs are supplied with the trigger.
The weight is not to be adjusted with the set screw. The set screw is only for adjusting the creep before the break of the second stage. Turn the set screw inward (clockwise) to lessen the creep. If you turn it too far, the second stage will vanish. Back it out just a touch, and you will have it perfect. It is
recommended to lubricate the triggers liberally with CLP. The use of Molly Slide on the hooks of the hammer and
disconnectors is fine, but not necessary.