lateral ridge 18 which terminates in an upper contact surface 19 which preferably is substantially a line surface of from about 0 0001 u2033 to about 0 005 u2033 in width 23 and from about 0 005 u2033 to about 3 16 u2033 in length 24 most preferably from about 0 01 u2033 to about u215b u2033 in length disconnector 14 is pivotally mounted on trigger body 35 by pin 54 and compression spring 37 has one end mounted in pocket 49 in the disconnector and the other end bearing against trigger body 35 as more clearly seen in fig3 a and 6 trigger body 35 preferably but not necessarily is formed with a raised slave portion 50 which can be readily machined ground to precisely adjust the neutral position of cam portion 16 without trying to dimension the whole under cut surface 51 of the trigger body 35 in a preferred embodiment the invention comprises a firearm trigger assembly having a receiver housing 15 a a firing pin hammer 30 pivotally mounted in the housing and having a hook 31 formed with a trigger engagement surface 32 a trigger 20 having a body 35 pivotally mounted in the housing and having a hook 21 formed with a hammer engagement surface 22 and having an under cut surface 51 a disconnector 14 pivotally mounted on the trigger body 35 and having an upper cam portion 16 a lower hook under portion 17 and an intermediate connector portion 56 forming a trigger body receiving gap 52 the disconnector having a center line 57 substantially aligned with a longitudinal axis of the firearm the hook under portion 17 being formed with a laterally extending ridge 18 on its upper surface the ridge having an upper.