Semi-auto rifles have been on the market since 1903. Yes 1903! Yet it was only when the mental institutions were closed down in the 1970s that mass murder really took off.
And for decades the anti-gun radicals claimed they ONLY wanted to register and ban HANDGUNS! “Rifles will not be affected!”
In 1981 Actress Lee Grant, on Good Morning America stood up, poked holes in the air with her finger and yelled....”THE NRA IS A RIFLE ORGANIZATION! THEY SHOULD GIVE UP THEIR HANDGUNS AND THEY CAN KEEP THEIR RIFLES!”
Then in 1985 came the first calls to ban semi-auto rifles. They have never let up on their calls for any type of gun bans.
Actually not quite true.
Lewis & Clark's 1803 expedition carried a Girandoni Air Rifle that was semi-automatic. It used either a .46 or .51 caliber ball and had a magazine that held 20 rounds. It was lethal out to 125 to 150 yards, and each air reservoir could fire ~30 times before it had to be replaced with a fresh one or refilled.
It was in service from 1780 to 1816, so before the 2nd Amendment was even thought about.
And I guess you could say it was 'gas-operated'. Air is a gas, right?