Gun store owners in the US state of Missouri say they have seen an increase in sales of the controversial AR15 assault rifle used in a Florida school shooting.

Some gun store owners in the US say they have seen an increase in sales of the controversial AR15 assault rifle since last week's Florida school shooting.

Calls for a ban on the weapon are growing after it was used by a gunman to kill 17 people in the school in Parkland.

In St Peters, Missouri, inside the Ultimate Defense shop, AR15s are on for sale and people are buying.

Owner Paul Bastean says it is no coincidence buyers are reacting to the sudden calls for gun control.

He adds that there is an abundance of the guns on the market.

Gun manufacturers reportedly overproduced them, anticipating a Hillary Clinton presidential victory in 2016 and possible gun controls.

Tim Holladay, owner of Doc's Guns and Ammo in Eureka, Missouri, says there is interest in the gun, which can sell for anywhere from $500 to a couple of thousand dollars.

He says he has had inquiries about the gun recently.

"It's a sporting rifle … we emphasise a lot of sport shooting. Well tell people everywhere, take up sport shooting, you'll love the firearm industry much more."