Sig Sauer has announced that changing the trigger in the MPX will NOT void the warranty, but there are still some things you need to know. The MPX has a higher recoil impulse than other ARs. There is a trigger bridge you need to understand before you start messing with your MPX trigger.
Sig Sauer previously released the following:
The SIG MPX has a fire control group specifically designed to accommodate the high impulse of the MPX operating system. The MPX Trigger Bridge (indicated below by arrow) is in place to reduce wear and extend the life of the factory installed fire control components. Removal of the Trigger Bridge is NOT recommended … While the SIG MPX fire control components are similar to the AR15 platform, and aftermarket fire control components may fit, installation is NOT recommended in the SIG MPX. Doing so may result in damage to the MPX proprietary fire control components or the aftermarket components you installed.
Thanks Ferrari Steve!
MPX photo courtesy of Sig Sauer