The Redding Precision Expanding Mandrel (0.2410") is a vital tool for long-range shooters and precision handloaders utilizing .243 Caliber or 6mm platforms. Designed to iron out internal case neck variations and eliminate minor imperfections left by standard sizing dies, this mandrel sets highly consistent, micro-targeted neck tension. By standardizing the inner diameter of your brass down to the half-thousandth of an inch, it optimizes bullet release forces, minimizes bullet runout, and helps lower velocity standard deviations for tighter groups downrange.