Shrouded Barrels and Moderators on Airguns
Jim Chapman
I have enumerated the advantages of airguns many times ,
and they are more or less in line with what I hear from the
growing numbers using airguns for hunting and pest control.
While each individual’s priorities may vary, one
consistently stated advantage is that airguns are quiet.
Depending on the type of gun and how it is configured, the
sound signature is typically far less than even a .22 subsonic

Airguns are quieter than firearms, regardless of the power
plant used. However, not all airguns generate the same type
or intensity of sound; the sound generated from a spring
piston airgun is at least partially of mechanical origin related
to the spring piston slamming home, these guns generate a
relatively small volume of air to drive the pellet forward
making them the quietest of the airgun power plants. The
release of a much larger volume of compressed air from a
PCP generates a louder discharge sound that is closer to a
firearm, though not exactly the same or as loud. Many
airguns generate velocities in the subsonic range, but at
higher velocities (around 1100 fps) a supersonic “crackâ
€� will be noted. Even in those guns with the potential of
going supersonic, the savvy shooter will often dial down the
power setting or use a heavier pellet to achieve optimal
ballistic performance at lower velocities along with a
concurrent reduction in the sound signature.

Beyond the intrinsically quieter discharge of airguns, they
may be further suppressed to a level that is truly amazing by
either using a silencer or a shrouded barrel. Before entering
this discussion there are a couple of legal issues worth
having a look at. A silencer that can be used, or modified for
use on a firearm comes under the jurisdiction of the BATF. It
is considered a firearm and must carry a serial number;
furthermore legal possession requires a federal permit. Unlike
the right to own a firearm, there is not a constitutional right
to own a silencer and not all states allow their citizens to
possess one under any circumstance. This license may or
may not be difficult to obtain depending on where you live,
and it will take a bit of time, effort, and a couple hundred
bucks regardless. If the airgun silencer and its parts can not
be used or modified for use on a firearm, then it should fall
outside of the jurisdiction of BATF and not require the
license. Many airgunners believe that an air rifle with a
moderator (silencer) permanently attached is therefore legal.
This is somewhat of a gray zone and the BATF in my
experience, does not always have a consistent interpretation
of their own regulations and guidelines. For shooters outside
of the USA, there are many airgun companies that supply
silencers as options and third party manufacturers offering a
range of aftermarket products. It is odd that in countries
such as the UK and South Africa that have laws which are
more restrictive overall, the use of an airgun silencer is
considered an almost essential piece of equipment. You
cannot buy these after market products here for the
aforementioned reasons, though there are a few rifle models
available that have a permanently attached silencer which are
imported and sold domestically. There are at least a couple of
companies looking at the manufacture of airgun silencers
from materials that would disintegrate under the temperatures
and pressures generated by a firearm, but to my knowledge
this is still in the early R&D phase and I don’t know if
the BATF will accept them as a work-around. I would not
recommend using an after market silencer on your airgun in
the States without the appropriate license, it’s not worth
the risk.

A developing trend that provides a very quiet gun while
fulfilling both the letter and the spirit of the law, are airguns
with integrated barrel shrouds. These are full length shrouds
that are built into the gun and provide a gas porting function
without an extraneous “device�, and are an integrated
component of the airgun. These are very effective in
reducing a PCP rifles sound signature, with the added
advantage of not substantially increasing the guns overall
length. There is an increasing trend by most of the high end
gun makers to offer models with integrated shrouds

In addition to the legal possession of devices used to silence
airguns, you also need to consider local hunting regulations.
Some states do not allow silenced guns for hunting, some do
not allow taking game animals but are OK for non-game
animals, and pest control activities usually get pretty wide
latitude. But be smart and check, don’t get yourself in
trouble and your gun confiscated!

OK, so once you get these details out of the way, how do
moderated guns work in the field? Two of the outstanding
hunting rifles I’ve been using for several months are the
AirArms S410 FAC, and the Rohm Twinmaster Air Hunter
Carbine, both .22 caliber and both shrouded. These guns are
more than capable of ¼� 50 yard groups, and can reach
out much further with the power to anchor small game while
generating a sound only a little louder than snapping your
fingers. On jackrabbits, prairie dogs, and ground squirrel
shoots, I’ve knocked multiple varmints over without
disturbing their neighbor sitting a foot away. Doing pest
control duty on a friend’s farm in South Africa that was
literally buried under a variety of pigeon species raiding the
feeders; we sat in camo quietly picking off multitudes of
birds without giving away our position. The advantage of
these quiet airarms for urban predator and pest control duties
are obvious, and opens up more shooting opportunity for
those that might not otherwise be able to participate in the

The majority of airguns I use when shooting and hunting
outside of the USA are silenced, and I find this especially
useful when hunting in more densely populated regions or
around livestock. I have a couple of airgun silencers that I
leave with friends in South Africa and attach to my rifles
whenever we head out for pest control around the farm. The
places I hunt small game here at home aren’t generally
that noise sensitive, but places where I shoot pest often are. I
like the fact that using a gun with an integrated shroud I can
be positioned in a field near a factory building with people
less than a hundred yards from me, and not be heard. There
is also a lot to be said for shooting moderated guns in my
basement range as well, the family can be watching TV or
reading upstairs and I don’t disturb anyone, plus I donâ
€™t need to wear hearing protection. I think that if you are
looking for a pest control gun or will be shooting in a noise
sensitive area, it would be well worth looking for one with a
fully shrouded barrel. If you will be using it to hunt small
game, just make sure of your local regulations. With no felt
recoil from the rifle, it is an awesome experience to shoot a
prairie dog at 75 yards and watch him through the scope
silently flipping off the mound!
Shrouded barrel on left and a threaded
propriatry moderator (right).
Disassembled moderator showing the baffles
which are the primary components in redirecting
air from behimd the pellet
Three methods of attaching a moderator;
propriatary threaded attachment on
moderator,(L), standard fitting for threaded
barrel (C), and slip on moderator attached by
tightening allen screws (R).
The three type of attachments being deployed
The Evanix Blizzard with an integrated
shrouded barrel effectively reduces the
discharge to a low level sound, and adds
minimally to the overall length of the rifle.