In TML note 1271 "Silencers" [email removed] writes:
>>>While the magnetic acceleration process of the gauss weapon may be ABSOLUTELY
>>>silent (and I have my doubts about this also), anyone within several hundred
>>>meters of the weapon will be treated to the staccato crack of gauss needles
>>>punching holes in the air.
>>
>> So what about sculpting the needles so that the air-flow around
>> then is radically different - ie it generates sound of a frequency
>> that is too high for the ears to pick up ? Obviously horribly
>> expensive to produce, but would it work ? Subsonic only, I expect ...
>
>It is also worthy to point out that a simple pillow when held against the
>muzzle of a gun, be it supersonic or subsonic, quiets the sound to the point
>that a person 20 feet or so away cann't hear it clearly. Admittedly we
>are talking about a single shot. But there are TWO things that cause the
>noise of gun fire. First and obviously, the expanding gasses of the burning
>gun powder, are easily quieted. Second is the bullet passing the sound
>barrior. Another easily solved problem. The only real hard part is making
>the silenecer have enough space to allow the compression wave to be absorbed
>and still have something that is small and light weight. That is why you will
>notice the larger/faster the round, the bigger the silencer. It would also
>be theoretically possible to silence a 155mm Howizer but not practicle.
I don't think I'd go so far to call the problem "easily solved", Dave, The
pillow idea (or any other means) still boils down to the same simple truth:
if you want a silent round, reduce it's velocity until it's subsonic. This
is not as easy as it seems (and for large, powerful rounds, like a .44 Magnum,
a pillow is not nearly enough).
A typical .357 Magnum round (w/ a 200 grain slug, which is roughly 12.9 gm.)
will have a muzzle-energy of 590 ft./lbs. (800 Joules), and a muzzel-velocity
of 1,158 ft./sec. (or 353 M./sec.), which is slightly above the speed of sound
(1,120 ft./sec. at sea level). Now, 2 simple formulas involving energy, mass,
and velocity (using the metric system) are:
(((E(j) * 21,630) / M(g))^0.5) / 3.28 = V(m/s)
- and - ((V(m/s) * 3.28)^2 * M(g)) / 21,630 = E(j)
where E(j) is energy (in Joules), M(g) is Mass (in grams), and V(m/w) is
Velocity (in Meters/Second). Given these formulas, and the fact that the
mass of the .357 Mag. slug doesn't change, then it follows that to make
the round's velocity drop below supersonic, we must reduce the total energy
of the round by 53.9 Joules (work it out for yourself). Since this equals
only about 2/3 the muzzle-energy of a .22 short, a thick pillow MIGHT do
the trick, but for more powerful rounds (anything in the high-powered rifle
catagory), forget it. And you still have the leaky cylinder to contend with.
Leaky cylinder? I'm glad you asked. Revolvers cannot be effectively silenced,
since a significant portion of the blast from the powder burning leaks out
at the interface between the cylinder and the barrel. Semi-auto pistols
don't have this problem, but the slide itself is extremely noisy as it works
(let the slide on an empty pistol slam forward and you'll see what I mean).
I guarantee you that it CAN be heard more than 20 feet away. Most silenced
weapons (both military and covert ops.) are single-shot pistols, firing
subsonic rounds. To be effective, they must be employed at close range
(less than 10 meters), and must be acccurately aimed at an un-armored part
of the victim. Sniper weapons (long range by definition) are never silenced,
as physical laws prevent the design of a weapon that is both silent AND
effective.
(Note: You can get the muzzle-energy/muzzle-velocity/slug mass data from
any Reloaders Handbook. Most sporting goods store carry them.)
Later,
"Look. All of this talking is getting us nowhere! I think we
should try a more direct approach."
"MY GOD!! THAT'S A HAND GRENADE!!"
"Right. It's faster than Imperial arbitration, and it hurts less."
Mark F. Cook
USMail: User Interface Technical Support
Hewlett-Packard - Interface Technology Operation
[address removed]
INTERNET: [email removed]
UUCP: {cmcl2, harpo, hplabs, rice, tektronix}!hp-pcd!markc