Madbull or Prometheus 6.01mm Tightbore - 6.01 since if its a DMR u might as well be shooting semi only
Systema Magnum Motor - High Torque motor for quick trigger response and maybe if u throwing in a stronger spring
I highly suggest you get a ASCU mosfet or a AWS Raptor Trigger FET for the active breaking, full cycle completion and DMR pre-cock mode 
and id also go with Firefly Hopup Rubber also maybe the mad bull hop up too