The UDP-9 and UDP-45 utilize the same pin setup as a standard .223/5.56 AR-15/M-4 and will work with any Mil-Spec fire control group. Most aftermarket triggers will work, however, some use a hammer design that is too short or a heavier hammer spring and do not reliably reset with a PCC BCG. Geissele, ALG & LaRue fire control groups have known compatibility issues with PCC bolt carriers. We do not recommend using any multi-stage fire control groups.
We do not have any testing data as to the compatibility of any binary trigger system nor do we plan on testing them. From our communications with current binary trigger manufactures, binary triggers are not compatible with PCCs.
We currently recommend using CMC Triggers pistol caliber trigger or Timney Triggers pistol caliber trigger if you desire an aftermarket trigger.