20 | SPORTING SHOOTER _ MAY 2018
Primers Not Likely
To Ma t t er
Q
I’ve been given a large lot
of new rifle cases that are
primed and a brand different
to what I’ve been using in my
.257 Roberts. It goes against
my Scottish ancestry to to
punch out and discard these
factory-seated primers and
replace them with my
standard brand. Will
changing primers have any
effect on ballistics and
pressure? By the way, acting
on your advice, my Roberts
has been long-throated and I
am using your loading data
with great success.
- Ian McIntosh
A
In rifle loads approaching
full power, I doubt if you
can measure any ballistic
difference in a hunting rifle
resulting from a change in
primer brands. That’s assuming
a change in brand and not a
change from standard to
magnum primer. Different
brands of primers do vary
somewhat in brilliance or
“hotness” and may occasionally
make a slight difference in
accuracy, but it’s usually so
small that nothing less accurate
than a heavy varmint/target
gun can demonstrate it. I have
never seen a particular primer
smooth out the performance of
a given load, nor have I ever
seen a primer raise the pressure
of a hunting load to a dangerous
level. I’m sure you can use the
primers in your new cases with
your standard load without
noticing a significant
performance change, if the load
was developed in the same
brand of brass.Ugh! A Chinese
Model 70?Q
Is there, or was there,
such a thing as a Chinese
Model 70 Winchester? I have
been told that a few copies of
this classic American riflecame to this country about 25
years ago. I have asked a few
gun shops and gunsmiths
about this, but they didn't
have any knowledge of such
a rifle. Most of them told me
to ask you! Can you enlighten
me, please?A
Yes, I saw one of those
Chinese Model 70s back
in 1991. Very few ever came to
Australia. It didn't impress me
one little bit, the way the bolt
cycled was less than smooth
and downright gritty when it
locked up. The finish was poor
and the stock was made of
some Chinese wood that didn't
have any appeal whatsoever. It
was manufactured by Norinco
in Beijing,in the People's
Republic and designated as
the Model 64/70. Like the
Norinco/Brno .22 rimfire
copies, it was pretty mediocre.The .30-06 Improved
Q
My mate and I have been
hunting together for
several years now using
identical rifles – a pair of
Ruger M77s in .30-06. But last
year my mate got his rifle
rechambered to .30-06 Ackley
Improved. He is loading itwith AR2209 and brags that
his improved rifle now
performs at 200 yards like it
formerly did at 100 yards. To
my knowledge he has never
had his rifle chronographed
with his improved handloads
so I am at a loss to explain
how he arrived at this
conclusion. What do you think
of the .30-06 Ackley
Improved? How much gain is
there in velocity?- Ken Barber
A
I built my .30-06 Ackley
back in 1980, measuring
the velocity of my loads with
an old Telepacific
chronograph which led me to
believe that there was quite a
gain in velocity. In 1992 I
repeated my tests using Re-
in place of the old H4831 and
clocked my loads with a new
Chrony chronograph. The
results verified that the extra
case volume really does give
the Ackley version a
discernable edge over the
standard .30-06 in a 600mm
barrel. This agreed closely with
what some other experimenters
have achieved. Velocities were:
3200fps with the 150gn bullet,
3100 with the 165gn, 2950fpsExtra case
volume really
does give the
Ackley version
a discernable
edge.”
ASK THE
GUN EDITOR TECHNICAL ADVICE FROM THE GURU – BY NICK HARVEYLetters containing questions for answering by Nick Harvey must be accompanied by a stamped self-addressed envelope.
Mail your let ters to: The Technical Editor, 3 Reef Street, Hill End, NSW 2850.
LETTER OF THE MONTH
Q
I am puzzled about how barrel
length relates to obtaining the
best accuracy from the .22 Rimfire.
Your reply to a reader’s letter
stated that a 457mm barrel gives
best accuracy with the .22 Long
Rifle cartridge. Why then do so
many target rifles have barrels
650mm in length? Is there a special
reason for this?- Nigel Watts
A
Target rifle barrels are made
longer for two reasons: A longbarrel adds weight and balance.
Two, it gives a longer sight radius.
Actually, some .22 rimfire barrels
are longer than necessary for the
cartridge. After a certain point,
which varies with each cartridge,
some velocity is lost due to friction.
As for accuracy, assuming the
shooter doesn’t need the extra
weight and longer sighting
radius, it’s possible to shoot
top match scores with
a short barrel, particularly
a thick one.Barrel Length For The .22 Rimire
.22 Long Rifle
efficiency peaks at a
barrel length of about
18 inches, but the
longer iron sight
radius afforded by
target rifle barrels
significantly minimise
errors for the shooter.