Worlds of the Imperium
Keith Laumer
Plot: A man is recruited to travel to a parallel world where his twin has become a ruthless dictator, and replace him. To help on his mission he is given a gun like you describe.
Full text of the novel available on Gutenberg.
I moved my right hand carefully, feeling for the pressure of the release spring that would throw the palm-sized slug-gun into my hand
with the proper flexing of the wrist.
The little weapon was a marvel of compact deadliness. In shape it resembled a water-washed stone, grey and smooth. It could lie unnoticed on the ground, a feature which might be of great importance to me in an emergency.
Inside the gun a hair-sized channel spiralled down into the grip. A compressed gas, filling the tiny hole, served as both propellant and projectile. At a pressure on the right spot, unmarked, a minute globule of the liquefied gas was fired with tremendous velocity. Once free of the confining walls of the tough alloy barrel, the bead expanded explosively to a volume of a cubic foot. The result was an almost soundless blow, capable of shattering one-quarter inch armor, instantly fatal within a range of ten feet.
It was the kind of weapon I needed- inconspicuous, quiet, and deadly at short range. The spring arrangement made it almost a part of the hand, if the hand were expert.
[...]
I moved back, dazed, dodging blows. I had only one chance and I needed
a dark corner to try it. Miche was right after me. He was mad; he
didn't like that smack on the jaw in front of the boys. That helped me.
He forgot boxing and threw one haymaker after another. He wanted to
floor me with one punch to retrieve his dignity. I dodged and retreated.
I moved back toward the deep shadows at the end of the room, beyond
Chica's pantry. I had to get there quickly, before the watching crowd
closed up the space.
Miche swung again, left, right. I heard the air whistle as his hamlike
fist grazed me. I backed another step; almost far enough. Now to get
between him and the rest of the room. I jumped in behind a wild swing,
popped a stinging right off his ear, and kept going. I whirled, snapped
the slug-gun into my hand, and as Miche lunged, I shot him in the
stomach, faked a wild swinging attack as he bounced off the wall and
fell full length at my feet. I slipped the gun back into my cuff and
turned.
"I can't see," a man shouted. "Get some light down here." The mob
pushed forward, forming a wide ring. They stopped as they saw that only
I was on my feet.
"Miche is down," a man called. "The new guy took him."
Gros pushed his way through, hesitated, then walked over to the
sprawled body of Miche. He squatted, beckoned to the man with the
candle.
He pulled Miche over on his back, then looked closer, feeling for the
heartbeat. He looked up abruptly, got to his feet.
"He dead," he said. "Miche is dead." He looked at me with a strange
expression. "It's quite a punch you got, mister," he said.
