One of the best kept secrets in accurate reloading is precise bullet seating depth. 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 just so-so accuracy and real tack-driver performance. The Lock N Load Gauge is universally acclaimed as the most accurate, easy-to-use and reliable method of obtaining that critical relationship. Hornady"s curved Overall Length Gauge is for autoloaders, lever action and pump action rifles. Uses Hornady"s modified cases sold separately)