A series of anti-gun events across the UK has kicked off a 100-day countdown to a United Nations conference on small arms in New York.
Outside Parliament in London, activists have been lying in a bath of fake blood to highlight the illegal arms trade.
Mick North, whose daughter Sophie died at Dunblane, joined a campaign meeting at Glasgow Cathedral.
The Control Arms campaign, including Amnesty International and Oxfam, is calling for stronger arms embargoes.
A report will be presented to the UN Security Council on Thursday, claiming that arms embargoes are systematically violated and calling for them to be urgently strengthened.
The Control Arms Campaign - a joint initiative by Amnesty International, Oxfam International and the International Action Network on Small Arms - says that every one of the 13 UN arms embargoes imposed in the last decade has been repeatedly violated.
And despite hundreds of embargo breakers being named in UN reports, campaigners say that only a handful have been successfully prosecuted.
In Glasgow, Mick North - whose five-year-old daughter Sophie was killed in the Dunblane school massacre 10 years ago this week - was joined by David Grimason, whose two-year-old son Alistair was shot dead in a Turkish cafe in July 2003.
The pair were accompanied by 41 campaigners, representing the number of people killed every hour from gun violence worldwide, who lay on the ground to highlight the human cost of arms.
Dr North said he welcomed Mr Grimason's involvement in the campaign.
"I know David well and he like me feels that we should not just look at things in the UK.
"Through the gun control work in the UK I have met people from other countries and it is obvious that guns are a worldwide problem, so when campaigns began to try and push governments to stop the gun trade I thought it important to add my voice.
"I think it's important that we don't just look at what has happened at home but appreciate what people suffer all around the world."
Mr Grimason said: "Arms control is close to my heart after losing my son, Alistair to a gun.
"My wife Ozlem and I have already been trying to persuade governments to tighten gun laws, and thus joining the Control Arms campaign is a logical continuation of those efforts.
"The campaign is incredibly important as gun violence is a worldwide problem, with the figures on gun deaths horrendous.
"It is our duty to work to tighten arms laws, but also our government's duty to do more to make an international arms trade treaty a reality."
Thursday's event was followed by a public meeting at Strathclyde University, at which both men spoke.
According to UK charity Oxfam, guns and other small arms are the world's deadliest weapons, killing more people every year than the atomic bombs dropped on Hiroshima and Nagasaki put together.
The activists are calling on the UK government to take action to support an Arms Trade Treaty, which they say would stop weapons falling into the hands of war criminals and human rights abusers.
UN bans on arms deals are currently in force in Ivory Coast, Liberia, Somalia, the Democratic Republic of Congo, Rwanda, Sierra Leone and Sudan.
Arms flows are also banned to members of al Qaeda and the Taleban and to any group or individual linked to those organisations.