Okay, some points,
1- It is not just the UK that has banned guns, Australia,(which is roughly the same size as the US by the way) banned its guns years ago, and while the US has more people, it also has a fuckton more police, so, you know per capita versus total and all that. Germany also has much more restrictive laws without flat out banning them, so there is another option. New zealand's laws are focused on the owner rather than the object which is a further option.
2- Criminals do not obey laws, this is true and a fact that is beloved by people who drop smug macros into discussions. However, if we stop and consider the actual ramifications of this, it becomes pretty goddamn irrelevant.
- If someone has an illegal firearm, that is a crime and they can be stopped there and then as opposed to simply letting them walk on.
- It will slow down or limit the permeation of these weapons (not eliminate, no one is claiming that it will eliminate them)
- Someone who fits the profile of a spree killer (isolated, angry, feels like they have been wronged) suddenly aquiring a weapon becomes a bigger red flag and they are more likely to be stopped.
- From what I can see, it is rarely career criminals that conduct these crimes and so average joe blog on the street is unlikely to know where to get a hold of illegal assault weaponry.
- Someone who is in need of mental help, and is likely to commit violent suicide by attacking those near themselves, is less likely to have a weapon to hand when they snap.
- Criminals, are, for the most part, profit motivated human beings. Someone who is already hiding from the law is not going to assist someone who will draw attention to themselves
- Criminals are often quite reasonable and are unlikely to support the person who is likely to gun down more than a dozen children.
- Not all people who commit these crimes use their own weapons, so if their friends and family do not own them, it is harder for the criminal to obtain it.
3- There is no need to immediately ban all guns, that is impractical, what needs to happen is a staged drawdown of firearm ownership, starting with making them illegal to sell, running buybacks and making it clear that, for example, your assault rifle will be illegal in five years time, but you have five years to obtain a weapon more suitable for hunting and will be provided proper training in the storage and security of your remaining weapons.