An “airsoft gun” is not to be regarded as a firearm for the purposes of this Act.
An “airsoft gun” is a barrelled weapon of any description which—
(a) is designed to discharge only a small plastic missile (whether or not it is also capable of discharging any other kind of missile), and
(b) is not capable of discharging a missile (of any kind) with kinetic energy at the muzzle of the weapon that exceeds the permitted level.
“Small plastic missile” means a missile that—
(a) is made wholly or partly from plastics,
(b) is spherical, and
(c) does not exceed 8 millimetres in diameter.
The permitted kinetic energy level is—
(a) in the case of a weapon which is capable of discharging two or more missiles successively without repeated pressure on the trigger, 1.3 joules;
(b) in any other case, 2.5 joules.