Generally, open the NICS system so anyone can run a background check on their phone, so that you don't have to travel an hour and pay $50 to some gun store who's going to do literally the exact same thing to run your background check.

Red flag laws are acceptable, if the hearing takes place before the person loses their guns. If someone's guns need to be removed right now, there's literally no reason a regular warrant won't work, and then charge the person with whatever charges they need.

Of course, both of those are compromises, and gun owners generally expect something in return for it. And no, "We didn't do worse" or "Well we let you keep SOME of your guns" is not compromise.

Assault weapon bans are unpopular because as much as people complain about them, handguns are used in far more crime, including mass shootings. They also almost always ban features that are solely cosmetic, rather than anything functional. Why does it matter if their banned if the difference is cosmetic? Because when it doesn't work, people will just try and ban more things.

This is at least changed when you suggest a semi auto ban, but those are unpopular because semi autos are the vast majority of guns produced in the last century. Seriously, the first commercially successful semi automatic rifle came out in 1905, and the technology is even older. Banning semi autos is nearly a de facto gun ban, when almost all guns owned today are semi auto.

Registries are unpopular, because they're seen as a major step on the slippery slope. Most gun owners perceive their existence to be entirely so that it's easier to remove guns when bans come down the line. While this may sound paranoid, considering Beto just turned the rhetoric from "No one wants to take your guns" to "Hell yes we're coming for them," well, it's not paranoia if they really are out to get you.

Now, most people will talk about arming everyone, which.... eh. I am a big fan of national reciprocity, where there's a national standard for concealed carry that all states must honor, but of course try and get that past people who support gun control. This is one of those compromises that might get you an Open NICS UBC though.

It's also pretty common for gun owners to want the NFA or the Hughes Amendment removed. The NFA requires you to register suppressors, short barrel guns, and machineguns. Suppressors are easier to buy than guns are, even in the states, in large parts of Europe, because their seen as a safety feature, and rightly so. They don't make guns quiet like in the movies, they reduce the sound just enough that they don't instantly cause permanent hearing damage. They're also less obtrusive when hunting, disturbing animals in a smaller area, and disturbing hikers and such less too. Short barrel anything is only in the NFA because they intended to ban handguns, and backed out because the political will wasn't there for it. The fact that short barrel anything is included the NFA is entirely procedural, that section should have been removed if they weren't banning handguns. Machineguns are pretty self explanatory. So removing the NFA is compromise that gun owners would love, but seems pretty unlikely to happen. Certainly, it seems unlikely that machine guns will be removed from the NFA, but suppressors or short barrel guns could happen, and would get the support of gun owners.

The hughes amendment may be a better compromise spot though. The hughes amendment closed the machinegun registry. If your machine gun was registered before May of 1986, it's legal. If I have a machine gun that was made in 1985, was perfectly legal in 1985, but didn't get registered in time, it's a felony to possess it. This was snuck into a law ineptly protecting people traveling across states(You have to go through a state in a straight shot, if you stop for gas or get pulled over your guns are now subject to the laws of whatever state you were in. Maybe the guns were legal, but the state you're from and the one you're headed for require you to have the guns in a locked case, while the state your currently in requires them to be in the trunk. Sorry, you're a felon now.) It was literally just a vindictive punishment for trying to pass anything helpful to gun owners, and it does nothing productive. Machine guns registered before 1986 are not less dangerous than any other ones. While an acceptable compromise for gun owners, I can only imagine the fuss from middle aged suburban moms, who already think you can buy machine guns at your local cornerstore. Seems unlikely to pass.

As far as what we can do to actually prevent these shootings? End the war on drugs, adopt a european style social safety net, adopt large scale focused deterrence policies, put heroin and other hard drug users in hospitals rather than jails. These things should reduce addiction and drug trade, which are the two primary motivators for violence in the US, increase police participation in communities, which reduces the number of police of shootings, and helps lift people out of poverty. Clearly, people who support gun control are likely to disagree with me, but I really think these policies, and similar ones, are much more responsible for the relative lack of violence outside the states than any gun laws.