By coincidence, I was just reading about how the M1 replaced the Springfield 1903 bolt-action because it was less tiring on the troops to keep up sustained fire with one.
"It was found that well trained firers, using the service rifle at 300 yards, could maintain a rate of fire of approximately ten rounds per minute, without an appreciable loss of accuracy, for a maximum periodof four minutes....all were temporarily incapacitated for further firing for a period of from six to ten minutes.
It was found that the same firers, using the two types of semiautomatic rifles at the same range, could maintain a rate of fire of approximately 16 rounds per minute, without an appreciable lost of accuracy for the same period, and without any evidence of physical fatigue....With an absence of malfunction, due to mechanical defects, it is believed that a rate of fire of 20 well aimed shots per minute could have been maintained for at least six minutes...without an appreciable loss of accuracy....
The men employed in the test had had almost daily firing, both in the regular target season and in the pursuance of these tests, for approximately two months, and were addition qualified as expert riflemen, so that the above results would probably two high for the average shot, and without the same amount of physical fitness.