If overhaul of America's healthcare system defined Barack Obama's first term, then the consequences of the massacre at Newtown may well define his second. Channel 4 News assesses his chances.

If overhaul of America's healthcare system defined Barack Obama's first term, then the consequences of the massacre at Newtown may well define his second. Matthew Moore assesses his chances.

By announcing a plan to bring in 23 separate changes to the ways guns are sold, administered, used and kept, Barack Obama is trying to halt the recurring horror of school shootings and gun violence in America, writes Channel 4 News producer Matthew Moore.

Perhaps the most ambitious of his measures is the ban on "military-style" assault weapons. The target of this measure is the AR-15, a semi-automatic rifle.

Automatic weapons unload bullets in a stream so long as the finger is on the trigger, whereas semi-automatics require one touch on the trigger for every bullet.

'Assault weapons'

For background, in 1987 President Reagan banned the future production or import of automatic weapons, the type held at waist level by pinstriped gangsters of the 1920s and shot into the air by jubilant Libyans.

But there remain 187,000 different models in circulation in the US.

Perversely, the Clinton ban on assault weapons popularised the weapons it sought to eradicate.

Then, in 1994, President Clinton signed off his own gun control measures, part of which banned "assault weapons" like the semi-automatic AR-15.

Unusually, that bill had a sunset clause, a 10-year expiry date. So from 1994 to 2004, not a single semi-automatic rifle or variant was legally manufactured or imported into the US. Millions were still owned and traded by dealers, and privately - but all legally.

Perversely, the ban popularised the weapons it sought to eradicate. The ARA-15's status as the must-have firearm was helped, too, by wars in Iraq and Afghanistan. Soldiers held M16s, which are simply automatic versions of the AR-15 - the civilian, legal, type.

Computer games played their part too. With adolescents firing off thousands of pounds' worth of virtual ammunition at a virtual enemy in seconds, some are not surprised that in a country where the guns are available, they do not at least consider getting the real thing when they turn 21.

Fierce opposition

So now President Obama wants to outlaw the semi-automatic rifle and other variations of it.

A ban on a weapons begins by banning the characteristics of that weapon, like pistol grips, so manufacturers modify the design to get around bans.

Hunting has near sacred cow status in the US as the acceptable face of gun ownership.

The president will find fierce opposition from the National Rifle Association and the National Shooting Sport Foundation, who long before Sandy Hook foresaw an attempt to ban their weapon of choice and started a campaign to re-brand it as a hunting rifle.

In one video a gentle-looking man holding a camouflaged rifle extols its light weight and well-balanced features, before suggesting that it will not be long before hunters refer to it as "Ol Betsy".

Not for nothing have they turned to calling it a "modern hunting rifle". Hunting has near sacred cow status in the US as the acceptable face of gun ownership. Hunters tend to be older, and politically engaged. They will lobby their representatives hard.

And it is on those representatives that Obama will be reliant to pass any legislation.

Who gets to have guns?

The second big aspect of the president's plan is most publicly popular. It is also the most effective. It seeks to increase the number of those who undergo background checks before they buy a weapon. Obama wants everyone buying a gun to undergo a background check.

In 1993 there were 18,253 gun murders, while in 2011 that number had fallen to 11,101. In that period the number of guns in American hands rose but the number of gun deaths did not. Bringing in thorough background checks was a contributory factor, but another reason was improved policing.

According to President Obama, 40 per cent of gun purchases go through no background check.

President Obama is banking on the theory that extending background checks will bring the number of needless deaths down even further.

it is not clear how he will do that. According to the president, 40 per cent of gun purchases go through no background check. He says this is because sales at gun shows do not require background checks. But, in truth, the bulk of those gun sales are done in private: in suburban garages, between friends, or via Craigslist. And at present they are entirely legal.

Only licensed dealers are required to comply with the background checks, and their numbers have almost halved in 20 years. So it makes sense that the sales are happening elsewhere. Unless the president changes the law to ban every single trade or transaction involving a gun between two private people, he stands little chance of actually ensuring that background checks become universal.

Appetite for gun control

The American public remains unconvinced that guns themselves are the main cause of gun violence. And while the appetite for tighter gun control laws is strong, with about 55 per cent of people saying it is necessary, that compares poorly with a poll conducted before President Clinton passed his gun control laws. Then, 70 per cent of the American public favoured gun control.

If Mr Obama is to win this gunfight he has to garner more support from the American people. And beware the potentially catastrophic mistakes that Democrats before him have made.

If gun people abhor anything more than anti-gun legislators, it is anti-gun legislators who do not know what they are talking about and who confuse different kinds of weapon and lump them all together. They view that as classic Democrat elitism, removed from the interests of ordinary Americans.

What the president has on his side is a vast network of ready-made campaigners. This week he launched Organising for America, which inherited his collection of networkers from his Obama For America campaign.

That is important because he is trying to reverse the flow of guns and a culture of violence. If he can do it, he could leave a Lincolnesque legacy for the 21st century.