Here’s an aftermarket trigger that doesn’t suck and actually shows some innovation. Iain Harris of RecoilTV highlights a few here and the reason why manufactures develop trigger system in the first place.
With all the customizing of AR’s , using a shorter barrel would need to also shorten the gas system to allow it to operate correctly.
Operating at this level the bolt carrier system picks up speed. Which winds up beating up the firing component.
The fire control components takes a huge beating, specifically the disconnector.
After four thousand rounds the pin shears and disconnecter failure occurs. This is the reason manufacturers comes out with trigger system to solve this problem and here’s one to consider.
KE Arms trigger system (tested with 5K rounds) built theirs without a disconnector.
Sources: Iain Harris of Recoil, Russel of KE Arms