British shooter Georgina Geikie failed to qualify for the final of the women's 10m air pistol at the Royal Artillery Barracks in Woolwich.
The 27-year-old, a part-time barmaid from Okehampton, Devon, finished 47th out of 49 competitors with a score of 359 from a possible 400 in the qualification round.
Guo Wenjun of China, the reigning Olympic champion, won the heat with a final total of 388.
Geikie will get another chance, however, when she lines up for her preferred event, the 25m air pistol on Wednesday.
And even a performance well below what she had hoped for could not dampen Geikie's enthusiasm.
"My target of experiencing starting an Olympic competition has been achieved," she said. "I feel like I've been there now and that I'm ready for Wednesday, which is my strongest event.
"I can't explain the emotions you go through so having experienced it now I'm looking forward to Wednesday. My performance did not match my ability in any way, shape or form, but it's all about maintaining what you can do under pressure and coping with those emotions.
"I tried to cope with them to the best of my ability but I'm afraid my score and my performance wasn't great.
"But it's a goal achieved by just standing there competing in front of an awesome crowd. I was in a complete zone of my own throughout my match but afterwards they gave me a big cheer.
"It's something I've dreamed of doing for years and years and trained so hard for, and I've achieved today what I've wanted to do my whole life. Today was not my main event, so it's about enjoying the experience and taking that experience forward to Wednesday."