The letters are pouring in to the headquarters of the 2.2 million-member National Rifle Association in response to a series of four controversial ads running in magazines like People, Better Homes & Gardens, Esquire and Boy's Life. The full-page color ads depict ordinary people of all ages--like Janice Schuler, who at 18 has been shooting for over a decade and practices nine hours a week--holding guns and talking about the joys of squeezing the trigger, safely.

Several thousand pieces of mail have come across the desk of NRA public affairs director John Aquilino--35, blue-eyed, bespectacled and balding prematurely--the person responsible for creating the million-dollar ad campaign.

"We're trying to correct the distorted view of who NRA members are," he says. "We're trying to change our image."

Aquilino, in the process, has changed his. A 1968 graduate of Holy Cross, with majors in English and philosophy, Aquilino--a Roman Catholic--was a conscientious objector to military service during the Vietnam war for religious reasons. And now he's promoting guns . . .

"This may be like trying to explain sex to a eunuch," he says, taking a deep breath. "I'm still the same person. After I got my C.O. status, I ran into a black Quaker on the Metropolitan Police Force. I was working as a cook at Clyde's. He put it all in context. I was asking him about carrying guns, and he went into a rather long dissertation on responsibility to the country not being at odds with his abhorrence of war.

"Suddenly I started to put the various pieces together. Holy Cross didn't prepare me to integrate theoretical reality with practical reality. There was very little discussion of the role of the individual in society.

"My basic beliefs about man's treatment of man haven't changed. I think what I did was right. I still have an abhorrence of war, of any bloodshed. I'm probably the most peaceful person you've ever encountered. I think the NRA is the most honest champion of rights in the country. It's totally compatible. The things that are so important to Italians--integrity, the family, living in a place where people can be together--that's what the NRA is all about."

What the NRA is all about in the ads is:

* Wally Schirra, one of the original seven astronauts, out in a field, shotgun cracked over his arm, saying, "Wally Schirra and his buddies want to be free to hunt next year and the years after that."

* Norma McCollough, wife and mother, who finds "competitive shooting very relaxing and personally satisfying," noting that "thanks to the NRA . . . my children will grow up with the same opportunity to enjoy the sport."

* Janice Schuler, a high-school senior who's been shooting competitively since age 7, admitting "it's been a sacrifice but . . . I've had the chance to . . . learn a lot about myself."

* Bryan Hardin, 8 years old, two teeth showing, out in the woods gripping his BB gun like a pro, announcing, "They need kids like me to grow up and keep shooting a safe sport."

"We've had very few negative comments," Aquilino says. "One schoolteacher said the ads were sick and perverted. A woman wrote that if Bryan Hardin is an NRA member, then he's a murderer just like the rest of us."

And then recently, Garry Trudeau ridiculed the campaign in the comic strip Doonesbury. "It could have been worse," Aquilino says. "Very pretentious. We'll get lots more letters because of that."

The precursor of the new NRA campaign came a few years ago when Aquilino wrote a print and TV commercial for the organization that declared: MEET THE GUN LOBBY.

"We had policemen, construction workers, farmers," Aquilino says. "It was quite successful. But not like this. We're getting two or three hundred members a week who want to be in the ads." Although they were Aquilino's idea, the ads were prepared by an Oklahoma City agency, Ackerman & McQueen, which has prepared campaigns for Daisey Air Rifles.

Aquilino himself became interested in the subject of gun control when he was writing a series on the topic for the now-defunct Washington weekly, Newsworks. "I realized," he says, "that people were being discriminated against because they liked guns. My reporting made me start to wonder: Is it curbing a political problem or a measure aimed at eliminating competition. I started working for the NRA in 1976. We have forever backed increased penalties for people who use guns illegally."

A native Washingtonian who recalls shooting seashells on the beach with a .22 when he was a kid, Aquilino now says he has come to enjoy hunting. "There's something about it that puts you in touch with everything that's right in the world," he says. "A sense of being at ease."