Hornady LNL OAL Gauge "Curved" Regulating seating depth and the resulting jump to the rifling is widely regarded as fundamental to improved accuracy. A few thousandths of an inch change between the bullet and the rifling can make the difference between average accuracy and real tack-driver performance. The Curved Model is for all autoloader, lever-action, or pump-action rifles. It also fits all bolt-action and single-shot firearms. It inserts into the chamber through the ejection port. It's not compatible with Adapter "D" or short-bodied cases.