Often, when trigger pill is "lightened" is done by reducing the amount of engagement between a trigger and sear, or sear and striker, or honing and inadvertently changing a critical angle, and/or cutting coils off a sear return spring. Learn what is a "bump test" and do it - make sure to yourself that your trigger is going to hold, until you trip it - do not want your rifle going off when you did not expect it to!!!
Some trigger designs have relatively clear "pull" settings - Kuhnhausen's Shop Manual (for Mauser rifles), page 97, says military mauser two stage triggers should not be set less than 4 pounds; Mark X Mauser triggers should not be set less than 3 1/2 pounds." He goes on, "A safe trigger is defined as one with a pull within the standard 3 1/2 to 5 pound range in an action that does not slam fire, impact fire or safety-off fire." All kinds of people claim to get much lighter than that with the mauser triggers - they are outside the design parameters - better to get a different commercial trigger made for that lighter range of pull, than trying to McGyver the original into something that it is not.