Yes. . .that was the ‘story,’ but when the capsule was discovered they found untouched the inside handle that he would have used to blown the hatch, thereby proving “the hatch just blew.” Additionally, “Astronauts who released the hatch in tests had to strike the release mechanism so hard they invariably bruised their hand, Buckingham said. At his post-flight exam, Grissom had no such bruise” . . .further; “In tests of the emergency release, Buckingham said, the door would be blown 25 feet out and 6 feet up. Film of the splashdown shows the door popped out only a few feet.”
http://articles.baltimoresun.com/1999-12-09/news/9912090197_1_gus-grissom-astronaut-gus-hatch Gus was not as depicted in The Right Stuff. He was a true hero.