Friday, January 23, 2015

Happy Birthday, John Moses Browning!

Colt Model 1902 Military, an early short-recoil pistol design from JMB.
So, the problem with a self-loading pistol is keeping the action closed until the bullet has left the muzzle and pressure in the chamber has dropped low enough that the brass case will be ejected neatly, as opposed to being transformed into a spray of shrapnel in the shooter's face.

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.
It would not shock me to learn that the two main parts of that toggle required more separate machining steps than an entire modern pistol slide. Further, the entire works were exposed to the great outdoors. Friend Marko once jokingly called it "The perfect handgun for a gunfight in a computer clean room."

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.
It is John Browning who actually patented the idea of extending the breechblock forward and wrapping the forward end around the barrel; this adds weight without adding a huge bulk at the back of the gun. In other words, JMB patented the one-piece slide and breechblock, which is to modern firearms what the wheel is to modern automobiles.

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.
This slide was locked to the barrel at the moment of firing by means of mortises on the underside of the slide into which fit matching lugs on the top of the barrel. The slide and barrel would travel rearward together for a fraction of an inch until a downward camming force, originally applied by a pair of swinging links one at the front and one at the rear, pulled the barrel down and arrested its progress, letting the slide continue rearward, extracting the the spent case from the chamber.

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.