Frenchman,
I am assuming you are talking about a single trigger? If so then yes as the guys mentioned above a little heat helps but usually they are soft. If it is a double set then you have to watch the fit of several parts, but e tail front and rear can be "adjusted" easily enough. The two trigger leaves in a double set are of a higher carbon steel and could easily snap without heat. If these are what you are wanting to adjust just heat sink the engagement part in the vice and heat and adjust as needed.
Jeff