I have a picture of an M14 dated September 14, 1961 that shows an M14 on top of a pile of 30,000 rounds fired in one day in the same rifle at the Springfield Armory. This was part of the standard testing for both the M1 and the M14. Impressed the heck out of me. It doesn't say if it was semi-auto or full auto-my guess was semi.
It was a 30,000 round endurance test. It was not completed in one day. It was a mix of semi-automatic and full-automatic fire. The rifle was cleaned periodically, I believe every 2,000 to 4,000 rounds. I think I have a report on it somewhere.
A 30,000 round endurance test was never part of the "standard testing" for the M1 or M14. This test was a publicity demonstration, necessitated by the number of quality issues from the users, which had gotten the ear of Congress. Springfield needed to show that the design was solid.
The M14 had a very unfortunate development, development delays, years of testing, delays in production, poor initial quality, and worst of all very poor public relations. Remember the Berlin crisis of 1961? Newspapers were full of pictures of US Army troops looking exactly like they did in WW2, 16 years earlier, while other NATO countries and worse the "Commies" armed with modern weapons....