Here is the trigger module:
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The adjustment screw at the front of the trigger guard adjusts general pull weight. There is a second adjustment screw, at the rear of the trigger blade. The tip of this screw (visible through the window directly above it, just to the rear of the trigger pivot) provides a secondary fulcrum between the trigger blade and sear "rocker" (not sure of the official name). When the trigger is pulled, these components eventually touch and the second stage begins.
If this screw is too far in, the transition to the second stage happens too soon and the second stage will be heavy and creepy. If it's too far out, there is no second stage at all, and the let-off is extremely light and vague. Better the former than the latter from the standpoint of safety for field purposes, IMO, but the adjustment is available.
Obviously, follow any and all appropriate procedures if one decides to mess with factory adjustments. If in doubt, leave it alone. Don't mess with systems that one does not fully understand.