To make progress, one must understand the other side. Most liberals and democrats have zero experience with firearms, and they support the current AWB and any future gun restrictions because they feel a need to protect schoolchildren from firearm violence, and because the media and friends they are surrounded by tell them it's a good idea.
They don't understand enough about guns to realize how stupid and ineffective the existing laws are, or how ineffective the newly proposed laws would be, because they don't have any friends to explain it to them. The best thing you can do is befriend a liberal and explain to them why the laws they are "liking" wouldn't actually work, and ALSO propose some logical alternatives for how to achieve the desired goal of protecting school children other than banning guns.
Democrats don't want to ban guns because they have some irrational hatred for guns. Rather, they want to ban guns because it's the only way they can think of to protect the children. If your arguments make sense, then you may be able to convince them that there is a better alternative, and maybe they will share that logic with their other friends.
First, it is important to have a suggestion for how to prevent gun violence in schools that doesn't involve banning guns, because you can't expect them to stand around and do absolutely nothing while this problem continues to get worse and worse -- and you also can't expect them to agree that arming school teachers is a solution to the problem, because honestly no parent wants their school to turn into some kind of military zone, and there is also a lot of deadly force by police in the media, so the idea of putting more gun toting trigger happy guards into schools isn't exactly comforting to most people.
Republicans also care about protecting their children, right? So there is no reason not to work together on this. I honestly don't understand why democrats and republicans can't work together on this issue, but the problem is nobody listens to the other side.
It is a well known fact studied by psychologists that every mass shooting inspires further copycat shootings. Before Columbine, no kid ever even thought of doing this....but once it was done, every disgruntled loser saw it as an option, and the more prevalent it becomes, the more normal it becomes, the more of a good idea it seems like...it's a way for those depressed kids to get revenge against the world, and to become famous. So, why not take this away from this? Why should they get to be famous? I would support a ban on the media from reporting any details about the shooter, such as his/her name, photograph, etc. This way, kids don't get to become instantly famous by committing a mass murder, and that may remove most of the incentive.
Secondly, it is important to educate democrats exactly why current and future gun legislation is or would be ineffective at preventing future mass murders. For example, explain to them the fact that the MA AWB does not actually ban "assault weapons" (which are already restricted by the NFA), but rather it just bans specific cosmetic features that have no effect on lethality (such as vertical foregrips, etc), as well as specific makes and models of guns (such as the AR-15 an AK), which are functionally identical and no more dangerous than any other common semi-automatic hunting rifle or handguns which are not banned. I have many liberal and democratic friends, and once I have explained this, they have never failed to agree that such a law is stupid and serves no purpose. Therefore, it is easy to get them to agree that, if any weapons should be banned, it should be because they are objectively more dangerous -- not because they have certain cosmetic features or nomenclature. That in itself would be a big win for gun owners who are constantly having to deal with ridiculous cosmetic restrictions.
Most democrats think they want to ban semi-automatic rifles, but not hunting rifles or defensive handguns. It must be explained to them that in fact, most hunting rifles are also semi-automatic, and equally dangerous...and also that having a shorter barrel on a handgun does not make it any less dangerous than a long rifle. If anything, I would argue that a handgun may be more dangerous, because it can be more easily concealed and brought into a public space. Once they realize this, it becomes clear that all semi-automatic guns are basically equivalent from a functional perspective, and banning any particular subset of semi-automatic guns would be completely pointless. Therefore, unless they think they can get bipartisan support to ban ALL semi automatic guns (which they know they can't), they might as well consider pursuing some other legislation that might have a better chance of actually saving lives (like, for example, my above anti-hero proposal).