That was his daddy’s rifle design. John Moses was good, but making that rifle at 3 years old might have been out of even his reach.
I went to the museum in Ogden once. There were some very old museum volunteer ladies watching the place. Way in the back was a WWI display with a 1917 and other goodies and a velvet rope in front of it. Shortly after I was there, someone walked in, leaned over, and plucked that fully operational belt fed machine gun off the display and walked out. I hope they upped their security after that.
Browning demonstrated the M-1917 belt fed machine gun to the Army. Linking belt after belt, he fed ammunition to it, and it fired, and fired. He topped of the water jacket in between attaching belts. Eventually after 45 minutes of continuous fire, he had exhausted all the ammunition. No stoppages. Nicht, Zero, Nada.
He then pulled out a handkerchief and tied a blindfold over his eyes. He disassembled the gun blindfolded, putting each part on a table in front of the assembled officers, down to the last part. He then reassembed it blind folded and performed a function check. It is important for soldiers to be able to perform maintenance on machine guns in the dark, without lights.
He did it again a few months later, because some of the officers thought it might be a trick.