I've also noticed a slight change in impact when shooting inside where the lighting is not as good as outside. I shoot without a peep (kisser only) but I wonder if looking through a peep in less than optimum lighting has something to do with changes in impact. Once in a while, I'll catch myself shooting to the left and notice I'm looking too far to the left of the string. On the next shot, I make sure my alignment is "tight" before I make the shot and,,,, perfect!