From the outside, the two barrackslike buildings tucked behind the G.C. Murphy's store in Hillcrest Heights look quite similar. Yet on the inside the atmospheres are quite different.

In one building, as many as 50 young, aspiring pugilists pound bags, spar, shadow box, dance and skip rope in excessive heat, literally fighting for the space they're standing on in the cramped quarters.

In the other half of the Hillcrest Heights Boys Club complex at 4104 23d Parkway, dozens of persons, mostly older women, gather in the air-conditioned luxury three nights a week tay bingo. Receipts from two of those nights finance the boxing club and other boys club activities.

Calling the numbers is Jim Merrick of Hillcrest Heights, who created the boxing club in 1960 with Humphrey DeCola. Merrick is emphatic when asked about his efforts for the boys 106 pounds and Freddie Tuttle, 18, at 147 were runnersup in the 1976 Olympic trials and at one time were rated No.1 at their weights by the AAU.

Frankie Burgess, 17, recently moved into the sixth ranking at 119: Bill Tuttle, 20, is rated third at 165 and Charles Tuttle, 17, only recently lost his eighth rating at 156.

Middleweight Wilbur Crews and heavyweight David Johnson became the first club members to turn professional. On July 2, each won his debut bout in Virginia Beach.

The club stresses hard work, using No. 1 ranking and the 1980 Olympics as goals, said Truman Tuttle, 51, the club coach for six years and the father of the three Tuttle youths. MOre important, he added, the club offers an outlet for its members, who range in age from 5 to 23.

"I have three of them wha re the nicest kids you've ever met," said Tuttle, who resides at 13711 Old Chapel Rd. in Bowie. "But I'm convinced, if they weren't fighting, they'd be in jail. They just have too much nervous energy to be standing on street corners.

"I've been coaching for 16 years and I've never had any trouble," said Tuttle, who recently coached a United States team that went on a 16-day tour of Finland, Sweden, Denmark and West Germany. "This is something I tell them before - if you're fighting in the schoolyards, fighting in the streets, stay away from here."

The fighters spend their evenings in the gym for a variety of reasons, though most indicate a strong desire to be No. 1. Workouts are held Monday through Friday from 6 to 9 p.m.

"I could be playing basketball or baseball, but in boxing it seems like you're getting somewhere," said Stewart, a resident of 1733 Willard St. in Northwest Washington. He is 5-feet-4 and weighs 116 pounds. "Boxing seems like the only sport where someone my size can be in."

"I get rid of my problems by beating the (punching) bags," said Burgess, who lives at 1821 9th St. NW in D.C. "It makes me feel liek a new man."

Freddie Tuttle said he has had many travel opportunities thorugh boxing that he would have never received otherwise. He also stressed that boxing was a good means of a person discovering his own worth.

"It's something I can do on my own. Here you can't blame it on anybody else and no one can blame it on you," said Tuttle, who has seen Scandinavia, Hawaii and Canda on boxing trips. "A lot of kids come down here thinking they're really something. But once they start boxing, they realize they're no better than anyone else."

Several of the boxer, such as Tuttle, work at the bingo some evenings. They appreciate those who play bingo for the money that is raised to help their club.

And the bingo players seem to have a high opinion of the boxers. Helen Wines of Hillcrest Heights runs the bingo food concession before slipping in for the final few games. She's become a big fan of the boxing club without ever having entered the gym. "I know them all. They come over here, in and out. If those little kid aren't the cutest things you ever saw when they come over to you like this," said the elderly lady, feigning a boxing stance.

"They never give any trouble here and I never hear of any trouble either. I think it's good, but it's one sport that makes me shiver. I'd hate to see them hit."