Lever Action, Rapid Fire, Paramilitary, Attack Shotguns.
These weapons of mass destruction that were created purely to circumvent the 96 gun reforms are not new. Lever Action Shotguns have been around since 1887.
https://en.wikipedia.org/wiki/Winchester_Model_1887/1901
There is no dangerous new technology here, the only difference between the 1887 and the newer versions such as the Adler are in the ergonomics of the gun in much the same way as you most likely have a more comfortable chair than your great grandpa had.
.50 Calibre Sniper Bullets .
The .50 BMG (Browning Machine Gun) is not new in fact it has been in use around the world since 1910 as a round for heavy machine guns. https://en.wikipedia.org/wiki/.50_BMG
contrary to the mostly Hollywood hype it is not an inherently accurate sniper round. It was designed to function well in WW1 machine guns, these machine guns were not needed to be particularly accurate the just needed to cycle well in the battle environment of mud, dust, sand and prolonged use. There are many, many rounds that are better suited ti precision long range shooting, but because Hollywood has a hard on for the old .50 you have probably never heard of them.
I’ll keep adding to the list as we go along. please if you have a gun myth, or some Hollywood BS i can add please post it below.