How a COP .357 Derringer works

The COP .357 is a 4-shot Derringer-type pistol chambered for .357 Magnum. The double-action weapon is about twice as wide, and substantially heavier than the typical .25 automatic pistol, though its relatively compact size and powerful cartridge made it an option for a defensive weapon or a police backup gun.

The COP .357 is quite robust in design and construction. It is made of solid stainless steel components. Cartridges are loaded into the four separate chambers by sliding a latch that "pops-up" the barrel for loading purposes, similar to top-break shotguns. Each of the four chambers has its own dedicated firing pin. It uses an internal hammer, which is activated by depressing the trigger to hit a ratcheting/rotating striker that in turn strikes one firing pin at a time. Older "pepperboxes" also used multiple barrels, but the barrels were the part that rotated. The COP .357 operates similarly to the Sharps rimfire pepperbox of the 1850s, in that it uses the ratcheting/rotating striker, which is completely internal, to fire each chamber in sequence.

Two complaints about the COP .357 are that it is too heavy to be used as a backup gun, and that the trigger pull is too heavy for rapid fire—even heavier than most modern revolvers.

https://en.wikipedia.org/wiki/COP_.357_Derringer

COP .357 Derringer: full disassembly & assembly
https://www.youtube.com/watch?v=SrG10mR1hJs

This video was made with the help of the game World of Guns: Gun Disassembly:
http://store.steampowered.com/app/262410/

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