ORIGINAL: Arthur P
By your own admission, you never check back to see if the guard is still centered. Instead, you quite properly concentrate on the target and pin, in that order. So, after you've centered that pin guard and gone on to the pin you want to use, you have no idea what happens.
Unless you've gone to extremes and trained your eye to do something totally unnatural, that pin is centered in the peep when you aim.
I know for a fact thats what I do. I'll center my peep on that housing and make sure my level is...well... level then both my eyes open up and I look at the target and nothing else. I have infact, found myself moving my head (gasp) on longer shots...and all I am doing is instinctively centering that pin in the peep. I have closed my left eye again..and found that the guard was no longer centered in the peep. But...as long as I do the
same thing everytime....it doesn't really matter what I do. All the peep is there for is to make sure I start off in the same place.