I have the 1/4" and in lower light conditions, my groups spread out more. Let meexplain a little...

The way I shoot is I center my circular pinguard inside the peep. I noticed that when shooting indoors (obviously in poorer light) that the outline of the peep is harder to see so my groups are not as good. It's almost as if the wall of the peep is too thin when there's not enough light and it (the peep)blurrs when I'm trying to focus on it. Anyone else have this problem?