Baton rounds, sometimes incorrectly referred to as rubber bullets or plastic bullets are in fact an entirely separate class of riot-control non-lethal weapon.
The basic idea behind a baton round is simple, use an explosive propellant to send a solid spin stabilised projectile in to a riotous crowd in the hope that the person hit will be disinclined to continue their unlawful behavour.
Quoting from hrw.org's "Why plastic bullets are wrong", original at http://www.hrw.org/campaigns/nireland99/bullet.htm
Plastic bullets are approximately 4.5 inches long and 1.5 inches in diameter. They weigh about 4.75 ounces and are made of rock-hard solid PVC (polyvinyl chloride). When a plastic bullet is fired, it leaves the barrel at approximately 160 miles per hour.
The projectiles and their launch mechanisms have have evolved rapidly since their inception - in line with personal grenade launchers - an item to which the baton round launcher is closely related. The original crude models worked by a large (about the height of a Coke can and around half the radius) lump of plastic launched from an adapted rifle by firing a live (ball) round into the core of the baton round. Lacking spin stabilisation and being exceptionally powerful these have resulted in many fatalities in the last 30 years they have been in use around the world. More modern baton round launchers feature optical sights, easier loading and spin stabilisation on the projectile to improve accuracy.
Try your hardest to avoid being hit by a baton round, I guarantee you won't enjoy it.
Update: 27th January 2003
Further reading of materiels from the web sites of UK police forces has yeilded the following facts.
some forces consider the baton round not
as a non-lethal weapon
but, to quote;
"The plastic baton round is a less lethal option than the firearm and can still cause serious injury or death.".
"The baton gun is an impact weapon. As with any use of force, including conventional firearms, it will effect individuals differently and its outcomes cannot be guaranteed to be the same on every occasion"
Injuries and Fatalities: Firstly, note that the baton round has had a long career. In the UK, where this noder lives, they have been in use since 1970 and have evolved considerably over that time. In Northern Ireleand there have been 17 fatalities directly attributed to the impact of baton rounds and 681 reported injuries. Baton rounds are almost certain to cause serious bruising, but their use is statistically much less likely to cause fatalities in modern times.
Authorisation to use: From my reading of what materiel is available, the use of baton rounds appears to be confined to two types of situation;
Riot situations, where the security forces (police, army) are under "sustained, violent and life-threatening attack". For example where the lives of law enforcement officers are under threat from petrol bombs, missiles, blast bombs etc.
Seige situations, where baton rounds may be used in place of lethal force.
Method of use: In crowd control/riot situations the target must be 20 meters from the firing point in order for that the strike to be of low enough force to not cause serious injury. In the UK the officers must have specific authorisation from their commanding officer (Assistant Cheif Constable rank or above) to fire.
Older baton rounds had to be fired at the ground "bounced" in to the crowd in order to be safe. No such resriction exists on the modern baton round guns, enabling their use against a wider variety of target positions. This also means that they may be fired more accurately.