The stock bold has a hard edge on the inside of the bolt that might break the paintball in some cases.  Well this mod will help reduce the breaks resulting from a hard inside hold edge. Materials: Dremmil tool
Just take the dremmil tool with the sanding piece on it and trim away some of the inside edge on the front of the bolt.  This will make the bolt cup the paintball a better so there is no edge to break the ball.  Make sure not to take too much material away, only a little to take away some of the edge. The finished product!