Gritty, Natural, Realistic Movies of the 1970s

You picked a poor decade for realism. The seventies is famous for movie makers with "contrived" grittiness to preach sermons. Just about anything Pacino was in, particularly the ridiculous Dog Day Afternoon which tries to make bank robbers appear humane and motivated. Don't believe that in real life. 

There have been some good picks, such as Killing Fields, but for the most part, the myth of the seventies is totally mythical, and a throwback to the days of Homer and the Greek hero. 

HANG EM HIGH actually has a lot of grit and realism, albeit in extravagant violence. Culpepper and Bad Company are mostly natural, but do contain a few mythical notes. 

Maybe the grittiest one is BURY ME AN ANGEL, a hidden gem that runs like a formula film, except there are twists that make it realistic versions of extravagant Hollywood, including the twist at the end. That would be my pick for "gritty, natural, realistic" movie of seventies. It's disguised till the end as something else.

There were some made for TV movies that just blew away the Hollywood formula films. THE INTRUDERS with Don Murray, John Saxon, and Edmond O'Brien fits this category for Westerns. LOST FLIGHT with Lloyd Bridges is a hidden gem about a crash on an island, and has a realistic touch that modern day geeks would hate.