The first 100 1st Differences of Prime Numbers.
Looks something like a musical score.
It should be possible to fire a potato cannon from a potato cannon, giving a two stage effect.
Slipping 1" ABS pipe inside 2" ABS would work, although I'd have to glue on a rubber strip as wadding.
Or go to a larger (4", perhaps) outer barrel, and a sabot style round?
Firing the second stage would be difficult, as a few fractions of a second delay would be needed. Perhaps a capacitor delay circuit, firing a ignition spark would work, and certainly would be light and simple.
It certainly would be dramatic, with a midtrajectory muzzleflash.

Perhaps I need a firing range.
(RenegadeMime suggests a leash.)
Learn something everyday...
Its been nesscary to mill a few logs for my house. Lacking a mill, I've been using my handy-dandy chainsaw.
Hoping to streamline the process, I do some research, and discover that I need a ripping chain to efficiently cut down the length of the logs. Ripping chains being prohibitively expensive, I made do with the ordinary chain. Rigging up a crude guide, and clamping a c-clamp to the bar's nose to keep the bar parallel with the guide, I struggled through the twelve logs I needed.
Roll Old Father Time around a year, and I need to cut a couple more. Being in a hurry this time, I just snapped a chalkline as a quick guide. I traced the chalkline with the saw, keeping the bar at a very shallow angle to the wood. Once I had a groove cut, I just kept re-traceing the groove, slicing deeper and deeper.
Long shavings were cut off, and it cut much faster then my plunging style ripping cuts had the year before.
The proverbial light bulb came on and illuminated a nasty excahnge I had read on a chainsaw mill forum.
Simply put, Guy A claimed that you had to have a ripping chain, and anything else was a waste of time. He had a
ripping chain and one of those clamp on guides that keep the saw moving accurately.
Guy B claimed that a ripping chain was not needed, and that he had split a lot of oversize logs down their length using his ordinary felling chain. He felt ripping chains were just an expensive refinement, and that Guy A was a shill.
Now if I hold the saw vertical to the surface of the wood, the teeth cut ACROSS the grain of the wood, cutting out tiny chips and generally cutting slowly. The felling chain has the wrong tooth angle and rake to effectively cut this way. But if I hold the saw so that it cuts ALONG the length of the log, it slices up the grain, peeling off two inch long shavings and cutting like a maniac. Now its possible that a ripping chain would cut at this angle even better, but the difference was night and day. Cuts that took ten minutes of struggle last year were whipped through in under two minutes.
Ironicly, the c-clamp bar guide was instrumental in preventing me from finding this cutting angle last year, and prolonging my struggle.
C'est la vie.
Its a Bad Sign when...
A mouse crawls out from under the hood of the car you just barely convinced to start, and stands there as an animate hood ornament. It stood and stared at me for a few moments, and then climbed back under the hood.
Damned gremlins.
The car in question ( a 1987 Volvo 740 Turbo Wagon) ran for twenty minutes longer, before dying with a horrid, terminal wheeze, a gasping rasp so pronounced that I am at a loss to understand what part could have generated it.
Perhaps the turbine's bearings?
Time for it to face the knacker; I've probably got six hours of parts stripping ahead of me.
Not that it really owned me anything. I paid 700$ at a junkyard for it five years ago, put another 700$ into it (mostly a new windsheild) and put 15,000 km on it. The odo stood at 386,000 when I bought it.Then when I replaced it with a marginaly newer car ( a 1990 Volvo 240 ), it still served faithfully for three years, hauling firewood every fall over old trails through the woods. Adventures included losing a muffler to an anthill (Thought it was a tuft of grass) and demonstrating that the bumpers can take a 30 kph collision into a large tree without body damage - a trick I wish my Dodge van could have emulated.
All things considered, it was the most comfortable car I've ever driven.

Rust In Pieces.