Load Development
John Haviland
E
very handloader believes that
by tinkering a few hundreds
of an inch with the distance
of the bullet to the beginning of the
rifling his rifle will magically start
shooting the nubbins off a button.
After experimenting with various
seating depths of bullets for a .223
and a .22-250 Remington, I can
confirm there is a sweet spot of bullet seating depth where accuracy is
the best in those rifles. However, the
only way to determine that agreeable spot for your rifle is to test it.
All rifles have different amounts of
wear in the leade, or beginning of
the rifling, and their chambers are
cut with reamers of slightly different
dimensions. Cartridges that fit and
shoot accurately in my .223 Remington might well shoot poorly or
even jam the bullet into the rifling
of your .223.
Determining
Bullet Seating Depth
Before experimenting with bullet
seating depth, you need to determine the cartridge overall length
(OAL), where a bullet’s ogive contacts the rifling. Several methods can
be used to establish this OAL.
One method is to make up a
cartridge with a bullet seated obviously long in a sized case with no
primer or powder. Fully chamber
the dummy cartridge into your rifle,
then extract it. Marks should be visible on the bullet where the rifling
engraved it. If these marks are difficult to see, the bullet can be first
coated with soot from the flame of a
stick match or candle. Carefully insert the cartridge into the chamber if
the bullet has a coat of soot, because
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LOAD DEVELOPMENT • Apr-May 2009
These .223 Remington cartridges have various bullet seating depths with Berger 50-grain Match bullets. From the left, 2.300, 2.970, 2.260, 2.200 and 2.175 inches OAL.
any contact with the feeding ramp
can leave false marks in the soot.
With definite rifling marks on the
bullet, turn in the seating stem on
your seating die a quarter- to a halfturn to seat the bullet deeper. Keep
chambering (and if need be, applying a new coat of soot) until there
are ever so slight marks of the rifling
on the bullet. Measure the cartridge
length, and that OAL is where that
bullet contacts the beginning of the
rifling of that rifle.
Another technique uses a fired
case, cleaning rod with a flat tip and
a fine tip marking pen. Take a fired
case and ever so slightly bend the
case mouth rim, just enough so a
bullet slips in with a bit of a push.
Make sure the fired primer is flush
or below flush with the case head
face, or an incorrect reading will occur when measuring final OAL. Slip
a bullet in the case mouth and leave
it protruding obviously long out of
the case. Gently insert the cartridge
into the chamber and close the bolt.
The bullet will be resting up against
the rifling. Slowly insert the cleaning rod into the muzzle until it
contacts the bullet tip. Mark the rod
at the muzzle. Remove the cartridge
and then close the action. Push the
rod into the bore until it contacts
the bolt face and then mark the rod
again. The distance between the two
marks is the OAL where that bullet
contacts the beginning of the rifling
of that rifle.
The easiest way to determine
where a bullet’s ogive contacts the
rifling is to use the Hornady L-N-L
OAL Gauge, formerly made by
Stoney Point. A modified case is
screwed onto the front of the gauge,
a bullet put in the case mouth and
the case inserted snugly into the
chamber. A rod inside the gauge is
slid forward to push the bullet into
contact with the rifling. The rod is
locked into place and the gauge removed from the chamber. The bullet will most likely remain stuck in
the rifling. A cleaning rod inserted
from the muzzle will knock it out.
Put the bullet back into the mouth
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Seating Depth and Accuracy
of the modified case and measure
the cartridge. That length is where
that bullet contacts the beginning of
the rifling of that rifle.
How much, if any, the OAL
should be reduced for the best accuracy depends on the rifle’s use.
Some target shooters (whose guns
have near-zero tolerance chambers)
seat their bullets contacting the
rifling, because they think the bullet
will enter the rifling straightly when
it is in firm contact with the rifling
at the start. Often, though, a bullet
will stick in the rifling when the unfired cartridge is removed from the
chamber. That’s not good for hunting rifles. Plus, at that long length,
a cartridge may not fit into a rifle’s
magazine. Many bullet manufacturers recommend seating bullets .03 to
.05 inch from contacting the rifling
for the best accuracy. A maximum
OAL has also been established for
each commercial cartridge. At that
length cartridges will definitely fit in
a magazine and chamber and extract
without a hitch.
I shot two rifles with cartridges
The Berger 50-grain Match bullets and W-748
powder were used to determine what OAL shot
best in a particular .223 Remington rifle. Ball
powder (or Hodgdon spherical), like W-748,
should not be compressed when seating a bullet,
because pressures can rise, which happened
with an OAL of 2.175 inches.
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The Hornady L-N-L OAL Gauge is a handy way to measure OAL where bullets contact rifling. A modified
case is screwed on the gauge, and then a sliding rod inside the gauge pushes the bullet into contact
with the rifling.
with bullets seated at various depths
to determine what OAL shot the
best in the rifles. The first rifle was a
Cooper Firearms Model 52 .22-250
Remington. This single-shot bolt
action has an extremely long leade
and some wear in the bore, so OAL
is 2.576 inches for Sierra 55-grain
BlitzKings to touch the rifling, more
than .2 inch longer than the 2.350inch maximum OAL established
for the .22-250. That long cartridge
length, though, makes no difference,
because the Cooper has a loading
pan length that will accept cartridges
nearly 3 inches long.
As the load table shows, the Cooper .22-250 certainly had an OAL
sweet spot of 2.546 inches. The
deeper bullets were seated from that
spot, the worse the rifle shot. I had
wanted to seat the Sierra 55-grain
BlitzKings in the .22-250 case even
deeper at an OAL of 2.200 inches.
However, that would have required
sizing the full length of the necks.
With only half of the neck sized
the full diameter of the bullets was
seated too far into the cases for the
necks to hold the bullets.
Note in the load table that average
velocity decreased as bullet seating depth increased. That’s because
a .22-250 Remington case has
more than enough internal capacity to hold 37.5 grains of Big Game
powder. With some room left over,
deeply seated 55-grain bullets do
not encroach on the powder space.
The deeper bullets are seated, the
more pressure and velocity go down
because the bullets have an increasingly unhindered running start
(freebore) before they contact the
rifling.
The Sisk Rifles .223 Remington
is based on a short-action Remington Model 700. This handy little
rifle wears a thin 20-inch barrel and
is intended mainly for hunting coyotes. This rifle is continually loaded
and unloaded. So an OAL that seats
the bullets into contact with the
rifling is impractical, because a bulApr-May 2009 • LOAD DEVELOPMENT
2
Load Development
The Cooper single-shot Model 52 has a receiver opening long enough to accept a .22-250 Remington
cartridge nearly 3 inches in length. For a rifle with a magazine, OAL must be kept short enough for a
cartridge to fit in the magazine.
let might remain stuck in the bore
when the rifle is unloaded.
An OAL of 2.300 inches set
Berger 50-grain Match bullets up
against the rifling in the Sisk .223.
As the load table shows, accuracy
at that length was so-so. The rifle
shot much tighter five-shot groups
when the bullets were backed off
the rifling .03 to .10 inch. Accuracy
went downhill significantly with the
bullets backed off the rifling .125
inch. No doubt that long jump allowed the bullets to enter the rifling
somewhat crookedly.
The load table shows the velocity of the 50-grain bullets remained
fairly constant with bullet OALs
of 2.300 to 2.260 inches. Velocity
dropped a bit with an OAL of 2.200
inches. However, velocity spiked
The Cooper single-shot Model 52 .22-250 Remington shot its best with an OAL of 2.546 inches.
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LOAD DEVELOPMENT • Apr-May 2009
with an OAL of 2.175 inches.
The 27.0 grains of W-748 pretty
well filled the .223 case, and bullets seated that deeply intruded on
the .223’s powder space. That was
enough to raise pressure sufficiently
to jump bullet velocity a good 100
fps.
Bullet Runout
A bullet seated crookedly in the
case neck will enter the rifling unevenly and may ruin an otherwise
tight group. So unless bullets are
seated straightly in the case to begin
with, it is a waste of time going to
the trouble of seating bullets an
exact amount from engaging the
rifling. I ran all the .22-250 and
.223 cartridges over an RCBS Case
Master Gauging Tool. In general,
the deeper bullets were seated into
the necks of .223 cases, the less bullet runout occurred. The opposite
occurred with the .22-250. That
might be just coincidence. I do keep
my reloading dies clean, as a buildup
of crud in the seating die can cause a
bullet to enter a case crookedly.
This experiment shows each rifle
has its accuracy sweet spot of bullet
seating depth. Some rifles are very
particular about this seating depth,
like the Cooper Model 52 .22-250
Remington. Others are more forgiving, like the Sisk Rifles .223. The
only way to determine that agreeable
spot for your rifle is to test it.
•
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