INSTRUCTIONS
Straight
& Curved
O.A.L.
Gauges
The initial distance a bullet travels is critical to an accurate handload. Any
loss of alignment, as the bullet travels from the cartridge case to the rifling,
will affect accuracy. Minimal changes in clearance (free-travel), between the
bullet and the rifling will often yield substantial improvements in accuracy.
The O.A.L. Gauge is an easy-to-use precision tool. It allows the user to (1)
determine maximum overall cartridge length (O.A.L.) from any firearm and (2)
produce handloads with a precise bullet seating depth while providing exact
bullet free-travel to the rifling. The O.A.L. Gauge will (3) monitor throat erosion,
and (4) check new or used firearms for freebore condition, a prime factor in
firearm accuracy. The O.A.L. Gauge uses your bullets for utmost precision.
The O.A.L. Gauge is sensitive and accurate enough that variations in operating
technique or grit and carbon in the throat can produce variations in your
results. It’s a good idea to clean the barrel before you begin, then spend a few
minutes to develop a technique that will produce a repeatable result. With a
little experience, it will take but a minute or two to determine a proper freetravel and resulting bullet seating depth with any bullet you select.
Modified Cases are required to use the O.A.L. Gauge. They are available from
Hornady to fit popular firearm chambers (see listing), and are kept within
SAAMI specifications. Wildcat, Ackley Improved, and tight-neck chambers,
require that your cartridge brass be factory “modified” for use with the O.A.L.
Gauge. To order, see procedure on reverse side. Modified Cases are threaded
at the case head to attach to the O.A.L. Gauge. The case-neck is enlarged to
allow your bullet to slip freely within the neck. Chamfer/deburr both the
inside and outside of the Modified Case mouth to enable bullet
to slip freely. If in doubt of the fit of the Modified Case with your chamber,
insert the case into the chamber, then close the bolt. It must close freely
without distorting the case. DO NOT FORCE.
We are sometimes asked about headspace variations between the Modified
Case and the chamber. Generally the variation is a few thousandths. Many
handloaders choose to ignore the variation, as the O.A.L. Gauge provides
a more meaningful result than they have achieved with previous methods.
However, it’s easy to measure headspace variations using your caliper and a
Max. Cartridge Gauge or a Cartridge Headspace Gauge (Hornady makes an
excellent one.) Simply compare your fired brass with the Modified Case, then
“factor in” the variation, if it’s significant. Handloaders desiring absolute
dimensions can have their fire-formed brass “modified” by Hornady.
Do not place Modified Cases in a media type polisher, as the media will
become lodged in the threads making it difficult to remove. Also, do not
outside neck-turn Modified Cases in an effort to fit a tight-neck chamber.
This will result in the neck I.D. becoming too small to accept a bullet, which
ruins the case. If required, case necks can be reduced with emery cloth. DO
NOT RESIZE!
It’s a good idea to measure your bullets for length uniformity with your caliper.
Severely damaged or irregular bullet tips will produce overall length variations
when measurements are taken. Variations of .010" or more will produce
irregular O.A.L. results requiring the use of a suitable bullet comparator,
described later.
TO USE THE O.A.L. GAUGE: Remove the bolt or open the action to allow
access to chamber. Thread-on appropriate Modified Case to the O.A.L. Gauge.
Insert a bullet, with undamaged tip, deeply into the case mouth. Insert
assembly into firearm chamber, then slide bullet adjustment rod (plunger)
forward until contact with the rifling is felt. Lock adjustment rod in place with
thumb screw. The bullet will most often “stick” to the rifling. To remove the
O.A.L. Gauge assembly intact, gently push the assembly out, using a wooden
dowel or cleaning rod inserted from the muzzle.
We recommend using no more than 3 or 4 lbs. pressure on the bullet
adjustment rod (about that of a light trigger pull). Then, gently tap the bullet
adjustment rod with your index finger to ensure the bullet is in light contact
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
loads. There are no short cuts in this area. However, once the optimum freetravel is determined with one brand of bullets, this same freetravel dimension
will most often be preferred with other bullet brands or weights. Remember,
if other bullet models or weights are chosen, they will have differently shaped
ogives, which will require that you repeat the O.A.L. Gauge process with the
new bullet.
While not absolute, there are several reasons for our free-travel
recommendation: (1) A more uniform chamber pressure is produced to start
the bullet down the bore. This reduces pressure “spikes” resulting from an
interference fit. The result is a more uniform velocity which produces accuracy.
(2) As the bullet is aligned in close proximity to the rifling, it will stabilize
quickly as it exits the bore. (3) Safety and reliability; a .020" to .040" freetravel produces reliable feeding and extraction.
CAUTION ... Often-times benchrest shooters, competitive shooters, and varmint
hunters will seat bullets closer than the above suggested free-travel in an
effort to gain a more accurate load. Use caution if you do so. This should only
be attempted by experienced handloaders … those familiar with the results
of this practice. A Bullet Comparator is required to measure such rounds as
the variation in bullet tips will produce inconsistencies in length dimensions,
which may cause an interference fit with the rifling. This, in turn, can produce
substantially higher (excessive) pressure with the loads you may presently be
using. Also, the bullet may become jammed in the rifling which could pull the
bullet from the case when unloading a round from the chamber. Remember,
seating bullets without freetravel (“on” the rifling, or “into” the rifling) will
require that you develop a new load with reduced powder charge, then work up,
or down, until you develop a load that is both accurate and safe. If in doubt,
recheck dimensions, or obtain capable assistance. Consult reloading manuals
for proper data and reloading practices.
The above being said, it’s doubtful that loads “on” or “into” the rifling will
result in accuracy improvements with hunting guns. Instead, we feel they
will result in a loss of accuracy. This is due, in part, to the variable chamber
pressures required to start bullets down the bore when the bullets have
an interference fit. Our belief is that some free-travel is always required to
produce an accurate load.
PROBLEM RIFLES. Some firearm magazines will not accept rounds loaded to
an O.A.L. as suggested by the rifling. In this situation, some hunters will load
a few rounds as determined by the O.A.L. Gauge, chambering these loads only
for the first shot. The backup rounds are loaded to lengths as required by the
magazine.
Some firearms (new or used) have excess freebore conditions which will
not allow bullets to be seated near the rifling, as the bullet exits the case
mouth before contacting the lands of the rifling. This may be due to the
manufacturer’s chamber throating practices, cartridge or bullet design
criteria, or the manufacturer’s viewpoint on freebore. Also, barrels become
“shot out” or “throated” after considerable use.
Some of the foregoing may be due to the firearm manufacturer’s need to fit a
wide variety of bullet models and weights into the barrel. We have no control
over this (we don’t build the guns) and cannot resolve these situations—only
identify them. Some alternatives to excessive freebore are: a change in bullets
(brand, weight, style, or ogive shape), re-chambering the barrel or re-barreling
the gun.
Remember that as the barrel’s throat erodes from firing, accuracy will
diminish. To restore accuracy, you should seat the bullets longer, to match the
erosion, using the O.A.L. Gauge.
CAUTION … After using the O.A.L. Gauge, always check the bore and remove
any obstructions before firing.
See readily available MODIFIED CASE listing on back panel.
SENDING BRASS FOR FACTORY
MODIFICATION
Your brass cases can be sent to the factory for
modification. This includes all sizes of centerfire style
cases, from 17 caliber to 50 caliber BMG, including
WILDCATS and IMPROVED brass (Caseheads smaller
than the 223 REM family will require a “Hornet Adaptor”
which allows you to attach these small cases to the O.A.L.
Gauge). We prefer that you send brass that has been
fired (fireformed) in the gun that you want the brass
to fit. We prefer that you DO NOT RESIZE THE FIRED
BRASS. This will ensure a proper fit with your chamber
modification.
Hornady will deprime, drill, and tap threads in the
customer’s furnished case, asa well as inside ream the
neck to a diameter that is .002" over the bullet diameter.
This is done so that the bullet will slip easily in the
modified case. The modified case will be packaged in a
plastic storage tube.
Any of your brass, including all wildcat sizes, can be
custom modified at our factory for use with either
gauge. Simply send us two fired cases by mail with $15
in a padded envelope – no SASE needed now – for quick
turnaround (call or visit our Web site for more information).
IMPORTANT:
Chamfer/Deburr all Modified Cases
before use!
DO NOT RESIZE MODIFIED CASES!
Modified Cases Available
17 REM
17 HORNET
218 BEE
221 REM
222 REM
223 REM
222 REM MAG
22-250 REM
220 SWIFT
6MM BR REM
243 WIN
6MM REM
250 SAV
257 ROB
25-06 REM
6.5 GRENDEL
6.5 CREEDMOOR
260 REM
264 WIN MAG
6.8 REM SPC
270 WIN
7MM BR REM
7MM-08 REM
7X57 MAUSER
284 WIN
280 REM
7MM REM MAG
30-30 WIN
30 TC
308 WIN
30-40 KRAG
308 MARLIN EXP
30-06 SPRG
300 RCM
300 WIN MAG
300 WBY MAG
7.62X39
303 BRIT
32 WIN SPL
8X57 MAUSER
8MM REM MAG
338 MARLIN EXP
338 RCM
338 WIN MAG
340 WBY MAG
35 REM
35 WHELEN
350 REM MAG
9.3X62
375 H&H MAG
416 REM MAG
450 BUSHMASTER
45-70 GOVT
17 REM FIREBALL
204 RUGER
6MM PPC SAKO
243 WSSM
240 WBY MAG
257 WBY MAG
6.5X55 SWEDE
6.5X284
270 WSM
270 WBY MAG
7X64 BRENN
7MM REM SAUM
7MM WSM
7MM WBY MAG
7MM STW
7MM REM ULTRA MAG
300 REM SAUM
300 SAVAGE
300 WSM
300 REM ULTRA MAG
338 REM ULTRA MAG
358 WIN
378 WBY MAG
6MM PPC .261
30/378 WBY
338 LAPUA
9.3X74R
375 RUGER
405 WIN
416 RIGBY
416 RUGER
450-400 3"
450 NITRO EXP
458 WIN
458 LOTT
450-400 3.25
470 NITRO
500 NITRO
3625 W Old Postash Hwy, 68803
P.O. Box 1848, Grand Island, NE 68802-1848
308-382-1390 • www.hornady.com
69007
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