Watch Bridget Kendall's report on guns and children in the US

Children are used to advertise machine guns

Earlier this week Mr Heston urged that the group's "I'm the NRA" image campaign of the 1980s be resurrected to counter some of the negative publicity.

The $5m campaign is set to begin with advertising in next week's issues of five popular magazines in the United States. The NRA already has a cartoon-style mascot, known as Eddie the Eagle, who they say teaches children about gun safety, not the glamour of guns.

But gun critics say the industry is now targeting children in its advertising not to protect them but in order to recruit them.

Gun expert generation

New research suggests that the next generation of young Americans are already becoming gun experts.

Dr May: the young know most about guns

At the central jail in Washington DC a recent study by Dr John May asked inmates to identify nine popular models. Unexpectedly it is the youngest prisoners, aged 15-24, who are by far the most knowledgeable.

"They knew immediately which weapon was which and they started debating which weapon is the fastest and which is the easiest to shoot with," Dr May said.

Constitutional right or plain wrong?

The NRA is a staunch defender of the Second Amendment to the United States Constitution which calls for a "well regulated militia" and says "the right of the people to keep and bear arms, shall not be infringed."

But some scholars argue the amendment was simply a safeguard against foreign invasion.

The group's 3.5 million members are seen as a strong voting bloc and the well-financed organisation regularly influences state and federal legislatures.

It has little trouble attracting powerful politicians to attend their meetings. Senator Trent Lott, the Majority Leader, is expected to be the keynote speaker at a banquet Saturday night.

The BBC correspondent Bridget Kendall says that even with the recent series of school shootings there is no real national debate in the US about the need to keep the guns away from children.