Hornady Lock-N-Load Overall Length (OAL) Gauges - Manual (Page 3)

with the lands. The most preferred method is to use the bullet
adjustment rod in one hand and a wooden dowel inserted through
the muzzle in the other hand, “sandwiching” the bullet.This allows
a positive feel as the bullet contacts and releases from
the rifling.
Remember to use the same pressure or “tapping technique” on the bullet
adjustment rod each time you use the tool. Keep in mind that you can “drive”
the bullet into the lands as much as .025" by using excessive pressure or a
“heavy-handed” approach. The key is to find a relatively light, yet positive
“touch point” of the bullet’s ogive with the origin of the rifling. It is from this
“touch point” that adjustments can be made in bullet seating depth.
This illustration shows the variable relationship of the bullet to the bore.
Chamber pressure, accuracy and firearm function can be affected by changes
as small as .005" in free-travel.
When removing the O.A.L. Gauge assembly from the chamber, often-times the
bullet will slip out of the case mouth. There is no need to repeat the procedure;
simply replace the bullet into the case-neck, where the bullet adjustment rod
remains correctly positioned.
With the O.A.L. Gauge in hand, you are now able to measure the maximum
overall cartridge (max. O.A.L.) that will fit your firearm with the selected bullet.
Place the fixed blade of your caliper in the measuring port on the O.A.L. Gauge,
then ease the traveling blade against the bullet tip. Remove all slack, then
take a reading. Record data for future use.
With the maximum O.A.L. now known, you can produce loads of the same
length or shorter, using your caliper and bullet seating die. Simply compare the
O.A.L. Gauge round with the initial rounds produced by your seating die, as you
adjust the seating die’s stem. The rounds produced should be made shorter
by the desired bullet free-travel; typically .020" to .040".
We strongly recommend the use of a
Bullet Comparator (compare-a-tor).
A comparator allows measurements
to be taken from the bullet’s ogive
instead of the bullet’s tip, providing
a much more reliable measuring
surface. A comparator is essential
when seating bullets closer than
.020" from the rifling, as bullet tips
may vary considerable (as much
as .020"). The Hornady Lock-N-Load ® Bullet Comparator is ideal for use with
the O.A.L. Gauge. It is designed to properly align the O.A.L. Gauge and bullet
ogive on your caliper, allowing precision measurement and ease of use (see
instructions furnished with Bullet Comparator).
USE COMMON SENSE WHEN SELECTING A BULLET
SEATING DEPTH. We recommend a free-travel (clearance) of .020" to .040"
between the bullet and rifling lands for hunting rounds. In our experience,
excessive bullet free-travel (over .040") will most often result in a loss of
accuracy. However, each gun will have its own preference, and it is up to the
handloader to determine the optimum bullet freetravel by range testing the