GTW
FEATURE
44 www.guntradeworld.com
I N - D E P T H W I T H C A L W A R D
Clearly, subsonic .22s are quieter than
supersonic .22’s and the supersonic .22 HV, .22
Magnum, Hornet, .223 etc cannot be made
silent. Th e 40 grain .22 subsonic bullet produces
about 40 ft/lb of kinetic energy. A 165 grain .45
bullet at 875 feet per second with fi ve grains of
pistol powder produces about 100ft/lb, which
is not exactly powerful – and a much louder
explosion that even a large, effi cient suppressor
struggles to contain.
However... Put the same bullet weight and
the same load of fi ve grains of pistol powder
and the same suppressor on a .308 and the
result is much quieter. We can’t put four
grains of powder and a 165-grain bullet in a
.22 but we can see that the .22 is the quietest
of the three, the .308 is a bit louder and the
.45 the loudest. A friend of mine jokes that
this is “Ward’s First law of Suppression – Big
Bore=Big Bang”. All other things being equal,
(bullet weight, powder weight, velocity and
kinetic energy) a large calibre bullet produces
a louder bang than a small calibre bullet of the
same weight.
Th at said, I’m struggling for a theoretical
explanation as to why. I’ve consulted engineers
who logcially say: the larger circumference area
of a .45 bullet produces a larger gap for gas to
escape through than the smaller circumference
area of a .22 bullet. Big Gap=Big Bang. Let’s
test that. Put a 4.5 bore can on a .22 or a .308
rifl e and there is no appreciable increase in
noise which the theory tells us there should be.
I don’t refer to decibel meter test results here,
as I fi nd them meaningless. A decibel meter
does not measure what the human ear hears
and, in the case of a .22, a decibel meter rated
the closing of the bolt and the ping of the fi ring
pin louder than the suppressed shot – logical
for a meter but nonsense for the human ear and
brain.
Th e corollary of “Ward’s First law of
Suppression – Big Bore=Big Bang” is “Heavier
Bullet=Bigger Bang”. A subsonic 400 grain
bullet produces a bigger bang than a 160 grain
bullet, as much more powder is required to
produce the same velocity in a heavier bullet,
producing more pressure and a bigger bang.
Ward’s Second Law of Suppression states:
“Some suppressor designs are more effi cient
than others”. Th is may seem a bit obvious but
it needs stating. Take two suppressors with two
diff erent baffl e stacks. A suppressor generally
consists of an expansion chamber followed by
a baffl e stack that allows gas to expand and
cool then confi nes it to prevent it escaping the
muzzle at supersonic speed. Th e fi rst suppressor
uses fl at baffl es and the second funnel-shaped
ones. Th e fi rst simply blocks propellant gas
while the second will “strip” propellant gas from
around the projectile and direct it backwards,
slowing the rate and temperature of escape. It
is in baffl e design that the serious researchers
surge ahead of the pack. A suppressor fi tted
with more effi cient funnel-shaped “gas
stripper” baffl es will generally outperform
others although the audible diff erence will
be less noticeable in .22 than in .45. It’s in
baffl e design that the perfect match of baffl e
confi guration to bullet shape, diameter and
velocity shows its advantages. Th is research
is expensive as it requires a lot of trial-anderror
and shuttling between a CNC lathe
and an experimental fi ring range using sound
monitoring technology. A baffl e design with
a particular angle or shape must be machined
and fi tted in a tube mounted on a gun which
must be fi red with a variety of powders
and bullet types and the results compared.
When the fi nal result has been perfected and
marketed ,the developer will want to keep his
research to himself and charge as much as he
can for his product.
Ward’s Th ird law of Suppression states: “Fast
Powders are quieter than slow powders”. Just
as the automotive engineer does not want fuel
exploding in his exhaust system so the ballistic
engineer doesn’t want burning propellant
coming out the muzzle of his suppressor.
Fast pistol powders are designed to burn in a
short pistol barrel while slower rifl e powders
may need 22 inches in which to be consumed
entirely. Muzzle blast is unburned powder.
More eff ective suppression is achieved when
powder has been entirely consumed well before
the projectile reaches the suppressor. But there
may be a confl ict between effi cient suppression
and accuracy. I have tested fast versus slower
powders in my .45 Long Colt Carbine and the
accuracy advantage lies with the slower powder
but it is also noisier.
Ward’s Fourth Law of Suppression states:
“Not all noise comes from the muzzle of a
gun so is more diffi cult to suppress”. When
four grains of pistol powder are ignited in a
.45 Long Colt case and a 165 grain .45 bullet
launches down the barrel at 500 feet per
second, there is audible noise at the breech of
the rifl e. Short of surrounding the breech of
a fi rearm with sound damping material this
noise is diffi cult to suppress. Further proof
of this phenomenon comes from self-loading
guns which are noisier than guns with locked
breeches.
GTW
WHO IS CAL WARD?
Cal Ward is a retired IT tutor, blogger and
former rifl e and pistol correspondent
with the Irish Shooters’ Digest. He lives in
Northern Ireland and his interests include
black powder, rifl e and pistol shooting,
bulletsmithing, history, short story writing
and hillwalking.
This remarkable still from a YouTube
video was taken using a suppressor with
a transparent tube. It shows the bullet
departing the muzzle followed by a blast of
hot, glowing gas that has become trapped in
the expansion chambers.
A modern suppressor fitt ed to a CZ Scorpion
submachine gun represents the modern trend
towards lighter, more compact suppressors.
This photo of a Sharps rifl e taken at dusk
gives some idea of the volume of hot gas a
suppressor has to cope with.
The famous De Lisle silent carbine
manufactured in Britain during WWII which
was based on a Lee-Enfield action and fired
a .45 ACP pistol cartridge. It used supersonic
ACP ammunition and a ported barrel to divert
gases into a shroud suppressor aft er which
both gases and bullet emerged at subsonic
velocities.
The T8 Refl ex suppressor from Jackson rifl es
fitt ed by Fabian Connolly on my custom-built
Swedish Mauser in .45 Colt.
NEXT MONTH – SUPPRESSORS PART TWO
/www.guntradeworld.com