When you compare a lighter trigger pull to a heavy pull......what is actually happening to promote accuracy? I am guessing that with a heavy trigger pull the human contact/influence is more pronounced.
FWIW,
I recently acquired a Winchester Hi-Wall in 375 H & H. Not exactly a "light" rifle. I put a 4.5 x 14 variable on it. I set it up on a Lead Sled II with 40 lbs of lead shot on a concrete bench at the range. A stable platform. I've not measured the trigger pull but I'd bet its over 4 lbs. Screwed to 14 power at 100 yds. I could watch the crosshairs move at least 1/2" downward on the target dot. As best as I could determine I'm using the ball of my right index finger and pulling straight back, not down. When I shoot off the same platform with one of my Sako's that have a set trigger that breaks at 9 0z, the shift is not evident.
YMMV,
GWB