According to Moats in Shot Talk 'Loading the Short Shells' (Shooting Sportsman Magazine Sept/Oct 2003) you can buy 'Trim Doctor' for about $30 from http://www.ballisticproducts.com/ or take a 5/8" dowel, make couple small holes a bit more than 2,5 inch from the end, and with a hammer drive an X-Acto blade through at slight angle.