A suppressor is a firearms accessory designed to reduce or eliminate the flash and report of the weapon's muzzle blast. This class of devices are often - inaccurately - referred to as "silencers", a term which leads to significant overestimation of their capabilities. Most suppressors are detatchable and mount to the muzzle of the weapon to which they are fitted but some weapons are built with inherent suppression (such as the MP5SD and the De Lisle carbine).
There are a variety of different designs for suppressors, some of which are more effective than others, but the general principle is that the propellant gases that form the muzzle blast are trapped in the body of the suppressor and then vented at reduced pressure and speed so that they make less noise - the flash is hidden as part of the process. Allowing for differences in design, the bigger the supressor the better as it will allow more space for gas retention - but then the user is obliged to deal with a weapon massively overloaded and unbalanced by a huge piece of tubing clipped to the muzzle. Most current designs compromise and partially suppress the sound of firing - the shot is still clearly audible but not as loud as it would have been unsuppressed and may sound less like a firearm being discharged. Rate of fire is an added problem - automatic bursts, or even rapid semi automatic fire can overwhelm a supressor, preventing it from working and (quite often) damaging it. For self-loading weapons that use the exhaust gases to cycle the action fitting a suppressor may also require the adjustment of the gas parts to allow for the difference in muzzle pressures.
Suppressors may be reusable or disposable - the disposable type tend to work through a series of rubber wipes which the round must punch through, although the various (and often cinematic) designs made from plastic bottles and foam peanuts belong in this category perforce as well. Even re-usuable designs tend to require frequent dismantling, cleaning and very careful reassembly to prevent fouling.
Obviously a lot depends on the type of ammunition being fired - high powered rifle rounds generate a lot of muzzle gases and require huge supressors: where they are fitted at all the normal intent is simply to make it harder to determine the firer's location. In addition a round fired at supersonic muzzle velocities will generate the usual "crack" as it breaks the sound barrier. To counteract this a supressed weapon should be loaded either with naturally subsonic rounds or with a "cold loaded" version of a supersonic one that contains less propellant and thus achieves a lower muzzle velocity. Cold loaded rounds may also interfere with the action of the weapon. It is possible - although not terribly effective - to suppress a shotgun. A revolver can only be suppressed if it is one of those that uses the neck of the cartridge to make a gas-seal between the chamber and the cylinder and such designs are rare.
As hinted at above there are a variety of strategies when it comes to suppression - the suppressor may merely aim to hide the point from which the weapon is fired, to disguise the sound of firing or even just to protect the firer's hearing1. A truly silent weapon is a massive undertaking and rarely attempted - the aforementioned De Lisle was, allegedly, onesuch2 and its contemporary the Welrod Pistol another. The De Lisle was a SMLE rifle with the barrel replaced with a substantial suppressor firing the inherently subsonic 45ACP round - a very large weapon to deliver a pistol bullet about fifty yards. The Welrod was also fairly large for a pistol and fired a .22LR round to very little effect, requring a highly skilled user to achieve an effective kill. Long term, alternative technologies such as coil guns may be a preferrable replacement to supressed conventional arms.
Legality varies - in some places suppressors are illegal or otherwise heavily … suppressed … for private ownership, mostly due to legislative panics and exaggeration of their effects. In others they are actually required for some purposes (such as vermin control) to prevent a noise nuisance.
Game and Story Use
- Note that the vast majority of 'silenced' weapons are still very noisy. PCs who understand fireams should know this, even if the players are Hollywood-addled. Be prepared to use skill rolls as required.
- Likewise that firing full auto on most suppressors - especially ones that aren't built in - is likely to damage the suppressor and/or the weapon.