Hornady Lock-N-Load OAL Straight Gauge C1000 is an essential tool to get the perfect seating depth on your handloaded ammunition, thus striking the perfect balance between your bullet and the rifling of your rifle. A good "jump" (the distance between the bullet's ogive and the point where it touches the rifling) is necessary for pinpoint accuracy, and this Hornady reloading tool allows you to determine the precise seating depth of your rounds for optimum jump. Hornady has designed the Hornady OAL Straight Bullet Seating Gauge to use specially made modified cases, which are threaded at the case-head. This modified casing design was the only way Hornady could achieve the stellar .001" accuracy variable on the reloading equipment. The straight edition of the Hornady OAL Gauge is designed for bolt action and single-shot firearms, and it's the most precise version of the tool. To get utterly accurate bullet seating measurements for a highly accurate round, use the Hornady Lock-N-Load Straight O.A.L. Gauge.