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How to Use the Hornady OAL Gauge

An overall length gauge is a tool used for firearms that helps improve the accuracy of the shooter. Repeated accuracy for a rifle depends in part on the seating depth of the bullet in the cartridge, according to Stu-offroad.com. The overall length gauge allows a shooter to optimize this depth, resulting in free travel of the bullet from the chamber to the rifling. Hornady states that most shooters use an optimal distance of 0.020 inches to 0.040 inches. Hornady does not recommend the use of the OAL gauge to achieve free travel distances of less than 0.020 inch.

Things You'll Need

Modified case
Dial calipers

Instructions

- 1
  Obtain a modified case that will fit the chamber of the firearm to be used. Modified cases are available directly from Hornady, the gauge manufacturer, in a variety of common sizes.
- 2
  Screw the modified case onto the threaded end of the OAL gauge. Once the case is secured, insert a bullet into the neck of the case.
- 3
  Remove the bolt from the rifle and tip the muzzle of the gun up slightly. Insert the gauge into the chamber, taking care not to let the bullet fall out of the modified case's neck.
- 4
  Push the gauge's plunger gently forward until resistance is felt. Maintain gentle pressure on the gauge so as to not lose resistance. Tighten the thumbscrew on the rear of the gauge to lock the plunger and bullet in place.
- 5
  Remove the gauge assembly from the chamber. If the bullet sticks in the rifling, use a wooden dowel or similar object to gently dislodge the bullet. Place the bullet back into the modified casing.
- 6
  Use a dial calipers to measure the distance from the end of the modified casing to the tip of the bullet. Take this measurement without loosening the thumbscrew of the gauge. The resulting measurement is the maximum overall length of the bullet for best accuracy of the type of rifle used.

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