Thunderflashes and bird scarers are not fireworks in the eyes of the law
Although confusing, they are completely different from what you and I call fireworks jimjim.
I'm curious as to the makeup of agricultural "crow scarers" these are essentially large bangers
These are usually blank shotgun cartridges, fired towards the ground. A multiple latch/barrel system avoids it being classified as a semi-automatic firearm. These devices are licensed alongside actual shotguns, an easy solution to a farmer who typically has a normal shotgun anyway; so I'm told. There are other systems but this is the one that I have seen before on a friends farm, and on a farm in France while I was rambling.
There are also similar anti-intrusion devices available to licensed public, by which a trip wire sets off a blank shotgun cartridge pointed towards the ground, and scares off potential burglars. There was a case when some idiot decided to load the barrel with fishing-line weights and point the device towards the trip wire. I'm not sure if these devices were made unavailable after that or not.
Military style "Thunderflashes" are also quite legally available. These are also large ground salutes.
No, they do not work like that, they are actually classed alongside distress flares and consist of two pyrotechnics subsystems. The first launches a second pyrotechnic device a long way into the air, this second device is what can be called a salute. The "bang" happens a bloody long way from the ground! (well a "real" Thunderflash is supposed to be like this, but I do recall seeing some devices for public sale like you mention that are called thunderflashes, but the term has been misused. I believe these are intended for things like battle re-enactments, the people which engage in such activity enjoy an exemption from the law, but it is still illegal to use it otherwise. They are also not as powerful as a proper thunderflash). The ones that you might be thinking of are called flash grenades, and these are NOT on general public sale. Thunderflashes can be likened to an over-engineered, hand-held air-b**b.
Edited by Andrew, 30 May 2007 - 12:01 PM.