Fred,
Both the forward and rebound action are controlled by the same spring. Actually, some trying to lighten trigger pull have replaced the single mainspring with a lighter one which then created a misfire situation where there wasn't one. Apparently most rifles have the correct tolerence balance for the system to work as designed  while others need this simple tune up to get that balance.

Lightening trigger pull is another project. I was closely examining  those surfaces but at this time I'm happy with the reliability and haven't the courage to attempt the lightening...and may leave well enough alone and probably never do it.