On August 1, 1966
Charles Whitman killed 18 and wounded 31, using the following weapons:
Remington 700 ADL (6 mm), Universal M1 carbine, Remington Model 141 (.35-caliber), Sears Model 60 Semi-automatic shotgun (12 gauge), S&W Model 19 (.357 Magnum), Luger P08 (9 mm), Galesi-Brescia pistol (.25 ACP), Machete.
I don't see any mention of an AR-15 or similar rifle being used for that mass murder. Just goes to show you that if there is intent to kill, it doesn't take a semi-automatic weapon to perpetrate the task. Yes, he did have an old M1 carbine, a semi-auto shotgun a Luger and a .25ACP, BUT most of the killings were done with bolt action rifle and a knife (family members).
Those that do not understand firearms consider all guns to be "assault weapons" and actually they "ALL" could be in the right (or wrong) scenario. It's interesting that one can purchase a standard looking semi-automatic 9mm rifle with a standard looking stock, but if they get the same rifle modified to a military style(appearance) stock, then it will surely be construed as an "assault weapon." A Ruger Mini-14 is a .223 cal semiautomatic weapon that uses the same round as an AR-15, yet we rarely hear of it as being labeled an assault weapon. FYI, the Mini-14 is modeled after the Military M-14 rifle.

Majority of noise out the barrel due to projectile vein pushed out small hole. No gun totally silent. Just reduce how far they can be heard.

Sound Suppressors suppress noise, it don’t eliminate it.

Yes, that is true in a semi-auto pistol. But in a revolver, it is not the same "closed system" and gas ALSO escapes out the side of the cylinder. That is why a suppressor does not work on a revolver...

I think the problem is that most people realize that legal gun owners are seldom the problem. Ban all the guns you want, and criminals and crazy people will get them by illegal means. That may mean that law-abiding people are LESS able to defend themselves and their families from the criminals and the crazies who have managed to get guns by illegal means.

Well, there are rubber bullets and sand that can be shot out of a shotgun and disable an attacker, but not kill them. It would be possible to engineer such a gun. The difficulty would be getting the gun makers to lower their profit margin by trying something new and getting gun owners to accept something new.

The 22 rimfire can be the choice of criminals because it is relatively quiet even when unsilenced. Its low velocity makes it also a good choice for adding a silencer.

The main problem is that mass shootings are INCREASING in the US, but not in countries like Canada, Australia, and New Zealand.

The Uvalde murderer obtain his weapons legally. The police were scared out of their minds to go in after him. Meanwhile the kids and teachers were slaughtered. Ban assault weapons, period.

You can buy a Byrum pepper gun, but I don't think they are very popular. Most people want a real gun for self defense. And, most of the teachers for the concealed carry firearm classes will tell you that a .22 caliper handgun is too small for self defense.

They ARE all factors, but difficult to change. It would be easier to change the law so that a person needed to be 21 to buy a gun. Also, all semi-auto rifles should no longer be sold in the US. Those involved in crimes melted down and others bought back.