The sear is fire control parts are all MIM in any new sig the older ones have much better parts in the fire controls.. I believe the old parts were EGW I seen somewhere all the new parts are all made by Indo MIM. I personally would replace the parts In a new sig if doing a trigger job.. If your gun was made previous to 2010 then should have the good parts in it from what I understand. After that the parts are all MIM. If revolution armory chimes back in he knows more..
Didn't say you couldn't do a good trigger job with the new parts just that I would replace them. As there not as good as they used to be.. And I woukd replace the parts as there not that much money.. And MIM Sears and hammers have a Tendency to lose there hardness when trigger job is done and sometimes don't last as long.. Colt Sears seem to be the only ones the smiths want to use for trigger jobs that are MIM Sears. The rest they prefer to just swap for bar stock Sears and hammers..