The part of the slide that nobody cares about (but should)
When a pistol fires and the slide cycles backward, there is only one piece of metal responsible for dragging the empty brass casing out of the filthy, superheated chamber. The extractor has to grip the rim of the cartridge with absolute reliability, pull it backward until it hits the ejector, and let it fly clear of the gun. While the job is simple, the mechanical geometry used to accomplish it splits into two completely different schools of engineering. You have the traditional internal leaf spring extractor, and you have the modern external pivoting claw.
To understand the difference, you have to look at how John Moses Browning designed the 1911. The 1911 uses an internal extractor. It is a long, single piece of machined spring steel that slides completely inside a tunnel drilled through the rear of the slide. Because it is a single solid piece of metal, it doesn't pivot on a hinge. Instead, the entire steel arm acts as a giant leaf spring. When a round feeds up from the magazine, the brass rim slides up the breech face and wedges itself underneath the extractor hook. This forces the long steel arm to physically bend outward against the wall of its tunnel.
The tension holding that empty brass casing against the breech face relies entirely on the metallurgical temper of that bent steel. If you want to adjust the grip on a 1911 extractor, you have to pull the steel arm out of the gun, wedge it halfway into the slide tunnel, and physically bend it with your thumb to change its resting geometry. You are manually setting the deflection. If the steel eventually loses its temper from thousands of heat cycles, it loses its tension, and the gun will start leaving empty brass in the chamber.
Modern service pistols like the Sig P226 or the Glock take a completely different mechanical approach. They use an external, pivoting extractor. Instead of a long piece of spring steel, the extractor is a short, rigid steel claw that sits in a cutout on the outside of the slide. It does not bend at all. Instead, it rotates on a vertical steel pivot pin.
The tension doesn't come from the claw itself; it comes from a separate, heavy-duty coil spring located behind the pivot point. When the cartridge feeds up the breech face and pushes against the claw, the front of the extractor rotates outward. This forces the back half of the extractor to rotate inward, heavily compressing that tiny coil spring.
This modern design separates the gripping surface from the tension source. Coil springs have a significantly longer cyclic lifespan than bent leaf springs, meaning a pivoting extractor can usually run for tens of thousands of rounds without ever needing tension adjustment. It is a true drop-in system. You don't have to bend the metal or file the locating pad to get the gun to run. When I am rebuilding a slide or troubleshooting extraction failures, I source my replacement claws, pivot pins, and high-tension coil springs straight from https://www.brownells.com/gun-parts/handgun-parts/handgun-slide-parts/ to get the lockup right. The 1911 extractor is an absolute work of art when properly hand-fitted, but the modern pivoting coil-spring design offers a level of mechanical consistency that is incredibly hard to beat.