The 'palm up' method is correct for any long gun with a charging handle on the side (M1 Rifle, AK47, etc.). The reason is clearly listed in the opening post so I can't see how anybody 'disagrees' or 'doesn't get it'. I guess if you never contemplated what it would be like in combat to be in a fire fight and have a stoppage of unknown cause - all you want is to rack that slide and hopefully resume firing - you forget your training and grab it the wrong way, when the hang-fire goes off and the slide hits the web between the thumb and forefinger and dislocates the thumb - well, that wouldn't be good. So to this day I rack the charging handle with the palm up for that reason.