Media playback is unsupported on your device Media caption American children in North Carolina explain why they love shooting guns

FBI statistics suggest that December is the busiest month for gun sales - why?

It's a cold Tuesday morning in Chantilly, Virginia, but Blue Ridge Arsenal buzzes like any busy store in December.

Music plays. The tree sparkles. Customers wish each other Happy Christmas.

There are some differences, though.

Firstly, Bing Crosby is drowned out by the bang-bang from the firing range, out back.

Secondly, the lights on the tree are made from shotgun shells.

It's Christmas at the gun store - come on in...

Image caption Mark Warner at the Blue Ridge Arsenal

When buying from a licensed dealer in the US, customers must pass an FBI background check.

Since 1998, when the system began, December has been the busiest month in all but two years (2008 and 2013).

For Mark Warner, the sales rep, the reason is obvious. "It's holiday giving," he says.

Giving someone a gun for Christmas may seem strange to non-Americans. But here, it's the equivalent of…?

"Diamonds," interjects Mark.

"I got customers who are husband and wife. She gets Louis Vuitton bags, he gets firearms.

"That's their gift giving to each other."

Patrick Hudgens is planning to buy his 16-year-old son a hunting rifle for Christmas.

He's looking at a lever-action 357, price $525. If he goes ahead, it will be the "fourth or fifth" time he has bought his son a gun at Christmas or birthday time.

Patrick taught his son to shoot with a BB gun, aged six. After "really drilling the fundamentals of safe shooting", he progressed to more powerful weapons, preaching caution all the way.

"It's crawl, walk, run," he says.

Now, he goes shooting "all the time" with his son, both competitions (the International Defensive Pistol Association) and hunting, usually deer.

For Patrick, originally from northern Michigan, it's a classic father-and-son activity.

"It was for me growing up, and for my father, and for his father," he says. "It's tradition in our family. It's great fun, a great bonding experience."

For him, and many other Americans, handing over a gun is no different to, say, handing over a football season ticket. Did he himself get guns for Christmas?

"Oh yes," he says. "And when you turned 11, my dad made a really big deal about your first shotgun.

"He would not buy a piece of junk - it was something that would be an heirloom, that you could hand down to your son someday."

Image caption The lights made from old shells

Like Patrick, Mark is happy for his children - twin 17-year-old girls - to shoot. They don't hunt, but they're allowed on the range if their school grades are good.

"To me, shooting is a thing I grew up with," says Mark.

"Rather than sitting in a house playing video games, my mother said get out of the house, be home before dark, and don't get too dirty.

"That meant fishing, swimming, target shooting, a little bit of hunting. Guns were a very important part of me growing up.

"My high school, student parking lot, there were trucks with guns in them. People were going hunting after school.

"But we didn't shoot each other. We didn't have gun violence at school. We respected guns and we respected each other."

Mark says when parents buy their child a gun for Christmas, it's usually a rifle.

"Primarily 22 caliber (small ammunition), low recoil, cheap to shoot, fun to shoot," he says.

"Ninety-nine percent of the time, it's for target practice. It's a thrill to see a young child hit a bull's-eye over and over again and see that gleam on their face."

So there's nothing strange about wrapping up a gun and leaving it under the tree?

"I hope they get me one for Christmas," he says, laughing. "That way I ain't got to buy my own."

Background checks

Before selling, the licensed dealer checks the buyer's background with the FBI by phone or computer

Checks are usually completed within minutes

People can fail the check for a number of reasons - for example, if they've been sent to prison

More than 275m checks have been made since November 1998 - with over a million denials

In America, it is legal to give guns to other people. But there are laws to follow.

Firstly, it's a crime to buy a gun for someone who isn't allowed to have one - that is, someone who would fail the background check.

If you want to give a gun to someone in a different state, you must do it through a licensed dealer, so the recipient is checked. In some states, you need a dealer no matter what.

In Virginia, you can give a gun to family or friends without them being checked. But the store is careful.

"Say John Doe wants to buy his wife a gun - he can buy it, go home, and give it to her," says Mark.

"We push them to paying for the gun, leaving it here, and have her come and pick it up. That way we can background check the person receiving the firearm."

It's not uncommon for Mark to turn down a sale, if he's not happy. "We ask a lot of questions," he says.

"If they slip up, or say something that doesn't make me feel comfortable, they're not getting it.

"People have the right to buy guns. But I have the right to refuse to sell to someone, based on how they make me feel."

Does that happen a lot?

"Oh, quite a bit," says Mark, who has worked at the store for almost 20 years. "The owners here will back us up 100%."

Media playback is unsupported on your device Media caption A guide to the weapons available in the US and the rate at which they fire

You need a car to reach Blue Ridge Arsenal - it's on the edge of a business park - but footfall is high.

One customer asks about gift vouchers (they're popular). Another wants to buy shooting lessons for his 19-year-old daughter.

At the back of the store, there are 20 lanes where people can practise, shoot for fun, or both. On different days, different groups get discounts.

Today it's law enforcement and military. Monday is ladies' day. Once a month, the local church comes here to shoot.

"It's kind of like bowling," says Mark.

In between dealing with customers, he tries to explain the Christmas sales spike.

"The husband says 'Hey honey, I want this new rifle for Christmas'.

"He's more likely to get it for Christmas, then during January, February, March, April whatever. Putting the word gift to it, he's more likely to get that firearm."