Not total shite, but there are some glaring omissions in it. It mentions Air Pistols, but does not define them, it mentions 'lethal' as part of the definition of a firearm, but again does not define lethal as any set power level. It mentions 'Capable' but does not define what that means.
But it's no different from many other acts of parliament - the Highways Act for example, doesn't define what constitutes a Highway (how bizarre is that!)