Add: A huge international study of gun control finds strong evidence that it actually works http://www.vox.com/2016/2/29/11120184/gun-control-study-international-evidence
Add: If we could prevent even half of the 30,000 gun deaths each year through some laws that are not overly restrictive, would it be worth doing? Federal gun control laws could reduce deaths up to 90 percent, study says http://www.csmonitor.com/USA/USA-Update/2016/0311/Federal-gun-control-laws-could-reduce-deaths-up-to-90-percent-study-says?cmpid=FB
More: Weapons that have "assault rifle" appearance were chosen around half of mass shooters. They are symbols and supposedly strike more fear in victims, and they have higher accuracy than handguns. You can get higher capacity magazines for handguns as well, such as the Glock 34.
We have mass shootings of 3 or more people every day in the US in high crime areas, so those statistics should be separate from the mass shooter phenomenon of terrorists and highly pissed off people who plan their killing spree.
While the rate of gun associated murders has declined in the US by around 43%, the rate of mass shootings has
The number of people owning guns has declined in the US, while individual gun owners own way more guns. We still have the highest per capita rate of gun ownership of anywhere in the world.
The association between banning weapons and mass killings isn't clear, although you could say they increase with availability of weapons. "...there were 19 mass shootings between 1982 and the time the assault weapons ban was put into place in 1994. From 1994 until 2004, when the ban expired, there was a similar amount of mass shootings — 16 — but there were nine in 1999 alone. What is striking is that in the eight years since this ban expired, there have been 27 shootings in the United States." So we have gone from 1.6 a year to 3.4 a year.
A complete ban on guns is not common, and not even necessary. In both England and Australia, gun ownership is still legal, but a permit is required, and a need for it has to be shown. Both of these countries have very low rates of mass killing (like 0).
Some believe that limiting magazine size to 10 or 12 bullets may be better than further regulating guns. But magazines can be changed very quickly, and were in the Orlando shooting.
In the US, we have a geographical patchwork of gun laws, often with weak enforcement, which means that even though guns are restricted in an area, they are still very available. Gun regulation has to be complete or not at all.
Most police officers in Scotland don't carry guns. How do they do it?
New Guiding Principles on Use of Force from the Police Executives Research Forum (PERF) http://www.policeforum.org/assets/guidingprinciples1.pdf