|Colt Model 1902 Military, an early short-recoil pistol design from JMB.|
Early autopistols relied on complex mechanical setups, like the well-known Borchardt/Luger mechanism derived from Maxim's toggle joint, to provide mechanical disadvantage against which the recoil had to work.
|Beautiful, but complex.|
So, what are our choices to hold the breech closed for that crucial fraction of a second? Well, there's spring pressure, but you can only add so much of that before the action can't be worked by human hands. You can also add weight to the breechblock.
|The three locking lug cutouts on the inside of the slide.|
|The barrel in battery. Note how the muzzle protrudes slightly beyond the front of the frame. The little metal key is all that keeps the slide from activating the shooter's dental plan, by the way.|
|The barrel is now fully to the rear and dropped down.|
Modern pistols usually dispense with complexity of separate links and locking mortises in the slide, instead just using a camming lug on the bottom of the barrel and a shoulder on the chamber that locks into the ejection port, but the principle is the same one Browning came up with in the closing days of the 19th Century.