One fairly frequent excuse that’s being thrown up for the onset of mass shootings in recent years is “the sudden availability of military-style, semi-automatic, high-capacity firearms.”
Large-capacity semi-automatic rifles have been available in large numbers to the US civilian market for more than 60 years. There has been no “sudden” or “recent” availability of such rifles, so the reason(s) for these mass murders must be found elsewhere.
Here are a few examples:
1940s: Caliber .30 M1 Carbine: First issued to US military troops in 1942. Nearly seven million produced for military, huge numbers released into the civilian market after WWII, and dozens of companies produced them for the civilian market as well. Used both 15- and 30-round detachable box magazines.
1940s: Caliber .30 M1 Rifle (Garand): First issued to US troops in 1936. Nearly seven million produced for military. Internal magazine fed by eight-round clips. Huge numbers have been, and are being released to the public through the Civilian Marksmanship Program beginning in the 1940s, and tens of thousands have been sold back into the US civilian market from nations which received them from the US government for wartime use. (Not really a "high-capacity" weapon, but it sure reloads quickly.)
1974: Caliber .30 M14 select-fire Rifle: First issued to US military troops in 1959, still in use with some units. Fed by 20-round detachable box magazine. Because of select-fire capability cannot be released into the civilian market. Many tens of thousands of semi-auto versions (called the “M1A”) were, and are being manufactured for the US civilian market, by several different companies, since 1974.
1973: Ruger Mini-14: Ruger semi-auto rifle based on the M14 design, but utilizing either the .223, the 6.89, the 7.62X39 (.30 cal) or the .222 caliber round. First offered to the civilian market in 1973. Choice of 5, 10, 20 or 30-round detachable box magazines. The Mini-14 and its variants are immensely popular, and it is certainly safe to say that, at the least, many tens of thousands have been sold.
The answer to why there have been so many mass shootings in recent years will have to be searched out somewhere other than “sudden availability.”
Anyone with other examples to add to the above list should feel welcome to add them to this discussion