I predict with confidence that banning more guns and gun-like things isn't going to improve matters any, undoubtedly the reverse is true. A ban on replica and air cartridge guns will have the perverse effect, given the strong market demand, of increasing the supply and therefore the carriage of genuine firearms smuggled in from eastern Europe.
Many of the converted replicas found at crime scenes in this country were already illegal in this country, and have been for many years, even when still inert and unmodified. The Home Secretary has wide-ranging powers to ban the import, sale and possession of such items by what amounts to an "executive order." Manufacturing a firearm without the appropriate Home Office license, which includes converting a de-activated firearm or replica to shooting condition, is illegal with heavy legal penalties available. Anything that spits bullets is a gun and therefore illegal however it was made. In actual fact, they're banning things that are already illegal and banned. I know this seems crazy but this is politics we're talking about.
BBC journalists have been confused during interviews with Home Office ministers because they don't understand why all replicas can't be banned wholesale. The politicians are perhaps mindful of the propaganda outcome: they're concerned about the press they'll get when it becomes clear they've banned children's toy guns in their frenzy to outlaw evil. The Home Office know that guns are mechanically simple devices that can be made with crude tools and techniques. Converting suitable replica or de-activated firearms simply makes it quicker and therefore cheaper to make guns because some of the work has already been done for you - however this isn't rocket science, a competent car mechanic can make a submachinegun. Guns have been made in prison workshops under the noses of the prison guards. Guns were made in Nazi-occupied Europe by resistance forces in spite of the best efforts of the Gestapo. Guns are made in the third world from scrap metal using hand tools. Take a look at P.A. Luty's The Home Gunsmith. Even so, the quickest and cheapest method for criminal organisations to acquire guns is via diversion from the vast stocks of military and police weapons and huge numbers of such weapons are available on the European black market due to the situation in eastern Europe.
The status of the Brocock Air Cartridge System (BACS) is worthy of special explanation. BACS was reasonably popular even before the handgun ban as a method of using a real handgun with air gun pellets (or re-usable nylon projectiles) for cheap training that didn't require a shooting range. However, the legal status of using your handgun in this way was unclear, almost all firearm certificates were issued with the condition that your handgun could only be used on a Home Office authorised shooting range - irrespective of whether you were using it as an air gun or not. The Brocock guns developed post-ban were made with machining cuts to the cylinder/chamber intended to prevent the chambering of live ammunition but allow the use of a version of BACS. Brocock has constantly worked with the Home Office to try and modify their product to satisfy Home Office requirements but, by their nature, the Brocock guns contain components you would need for a real firearm and so are a good start for the manufacture of an illegal firearm. Even so, government claims of the use of converted replicas and air guns in crime are largely assertions that reveal nothing about the true state of the supply of firearms to the criminal classes. The Home Secretary can ban Brococks (or pretty much anything else resembling a firearm) simply by signing an order declaring the item "specially dangerous" under the terms of the 1968 Firearms Act so he doesn't need any new laws. (That would have the, undoubtedly minor, political disadvantage of alienating law-abiding owners whose only legal option would be to hand in the legally-purchased guns during the gun amnesty or destroy the air guns themselves.) It's hard to see how eliminating Brococks will stop people manufacturing illegal firearms. However, some criminals who would have made do with unmodified Brococks for the intimidation factor of what appears to be a firearm, but is actually a restricted-power air pistol, will likely simply adopt (criminals often rent guns from underworld dealers so one firearm may be used in a large number of unrelated crimes by disparate people) an illegally imported or manufactured firearm as their weapon of choice if Brococks become unavailable. This is hardly an improvement from the point of view of the person at the business end. Even if the criminal carries the firearm unloaded, it will still increase the demand for black market firearms and therefore encourage black market entrepreneurs to smuggle or manufacture more illegal guns and boost the supply. Arguably in the "best case scenario" these people would likely substitute knives for guns - that doesn't make me feel any safer (it's a winner for the armed police though - "first rule" applies).
Still, the proof of the pudding is in the eating. Will "controls" on replicas reduce the levels of firearms availability and use in violent crime? Observers will have to view the government statistics with scepticism. On the one hand, more laws "controlling" guns and gun-like items will in and of itself create more crime and criminals. On the other hand, the government will work hard to "adjust" the crime figures to get "a true reflection of the situation" - for some definition of "true." Stats to watch for if you can get them that are a real indication if they're genuine (and as opposed to what the BBC propaganda machine decides to tell) are:
That last statistic, military and police weapons gone AWOL, is impossible to get but I'd surely like to see those figures. By "unaccounted for" I mean, for instance, discrepancies in the number of guns listed as unserviceable and sent for disposal and the numbers actually disposed of. Creative accounting of various sorts can conceal a multitude of crimes for those in a position to do it and in the end we can only estimate the magnitude of this problem. (According to official figures, approximately 200 firearms are stolen from the military per year in the UK.)
None of the above tells you the picture about violence in society overall for those of us who don't have a fetish about the use of guns. (What is it with the policemen: Nazi helmets, rubber masks, black uniforms and big boots, weapons with every conceivable bolt-on accessory - fetishism or what? See, SAS trainers denounce `gung ho' armed police.)
As to what effect the increasing of the penalties for being caught in possession of a firearm will have, the above statistics will be a good gauge of the real-world effect. I'm skeptical that criminals wander around believing they might be caught. Conceivably it could lead to more shots being discharged at police officers as criminals become more motivated to resist arrest, figuring they'll get pretty much the same sentence whatever.
Former New York Mayor Rudolf Giuliani (notorious as "The Mafia Mayor" because of his dual role of federal prosecutor of Mafia suspects and having relatives linked to organised crime) is flavour of the month in the UK with his "tough on gun crime" stance from New York. Giuliani emphasises the "crime control" measures he instituted. What Giuliani doesn't mention is the important demographic changes, that were independent of government action, that were a major factor in changes in New York's crime rates. In fact crime went down in cities all over America during the same period, whether Giuliani's policies did anything important is highly debateable. The truth is out there - but it's hard to find.