Printing revolution

The machine printed 3d-weaponry.  You put the plans in at the thin end, and then it whirred into life.  Two arms whisked backwards and forwards, one racing across the full width of the plate, and the other edging along the length controlling where the first arm was depositing.  Over a period of about twenty minutes the weapon would be built up from the ground upwards, all manufactured from the deposition material.  When the arms slid back into their housing, a steel-grey box with the twisty dials, little LEDs and tiny, almost-hidden buttons, the protective cover would retract back like the roof of a convertible.  A puff of white vapour burst out of the top, and Tim's hand pressed warningly across my chest, stopping me from reaching for the weapon.
"Wait for it to disperse," he said.  "It's not exactly toxic, but you'd be coughing for a few days.  It'll kind of set inside your lungs, and it's not easy to break-down."
"Why do you use it then?" I said.  I was more interested in the gun on the plate; it was china-white and perfectly smooth.  Even its edges had a slightly blurred look to them as though it had been melted briefly once.
"Because it's the best material for the job," said Tim.  He went on to tell me about its tensile strength, its heat conductance and other technical aspects, but his hand had dropped by then and I was studying the gun.
It was slightly lighter than I'd expected, and slightly light for its size overall.  I picked it up, noting that it was very slightly warm, perhaps a fraction or two about body temperature.  As if it had actually hatched from an egg, or something organic like that, which fitted rather well with the slight blurring of edges I'd exepected to be sharp.  It was like the gun had been born.  Its grip was a perfect fit for my hand, and as I curled my fingers around the stock the grooves were in exactly the right place.  It felt comfortable instantly, and if I moved my hand a little, the gun seemed to fall back into the right place with barely any effort at all.  I checked the magazine: it needed a little tug to pull it free, and there was a soft cracking sound and another puff of dust when I did so.
"It can't be laid down as a completely separate piece," said Tim, noticing the puzzled look on my face.  "So it's actually built as part of the gun, just with very thin joining edges that break when you try and pull it free.  It'll slide in really easily now."  I checked, and he was right.
"Ammunition?" I said, disappointed to find that the magazine was empty.
"You buy your own," said Tim  "Like I told you, if anyone asks me about this it makes replicas, not real weapons."
"Could you print ammunition?  Like you did the gun?"
Tim shrugged.  "I don't know that we've got the right materials for that," he said.  "You want different characteristics for a bullet or a missile really.  I rather suspect that printing bullets would produce something too fragile to be fired, so you'd end up with the bullet exploding in the gun."
"Booby-traps, then?"
"Not from me," he said, his face serious now.  "You buy your own, kiddo."
I looked at his machine, the one that now promised to make our dreams of revolution a possibility.  Printed weapons meant we could get the cash together to get more printers, and print bigger, better weapons.  With no limit on the weapons, and the ease of buying ammunition, we could launch the revolution from several cells at once, rising up around the country and acting swiftly to neutralise the government before they had time to understand what was happening.  The revolution would succeed!
"Tim?" I said, finally realising why the machine looked odd.  "What's that dial? I pointed.
"Number of copies to make," he said, barely glancing.
"So why does it start at 0?"
Tim looked at me, and suddenly his grey eyes seemed unnaturally large and dark.
"Oh, I wish you hadn't noticed that," he said.