We've kicked this around before and I confess I still can not understand why fouling a bore works to cause consistency from shot #1 in many MZ's. I've heard barrel pressures rise due to sabot or bullet friction fouling causes in the bore. I swab with both sides of a damp patch then both sides of a dry patch between all shots (after that first fouled barrel shot). How dirty can the barrel be on shot #2 for example, after I've swabbed? Is it fouling in the grooves? The lands can't be very dirty on #2. Is it the oil residue from cleaning that's the shot #1 culprit such that the heat and debris of a fouling shot renders the bore less slick? I dry swab the oiled barrel before shooting but that doesn't bring shot #1 in line with the rounds that follow. I must shoot a squib load (no bullet) and foul the barrel.

Anyone know the "science" behind fouling a bore?

Anyone ever drop a bore light down the barrel after every shot/swabbing and take a look?