SHTF anti-materiel idea

  This is one of those headache-inducing ideas that folks like the BATF really hate, since technically it's legal under many firearms determination findings and regulations, but could probably be attacked as a "destructive device" which is a handy legal umbrella term for "anything we don't like".

 And there are good reasons not to like this.

 Fortunately, we are unlikely to ever see bands of roving bandits brandishing these things because A) it's not very portable - more like a crew-served weapon but without all the big bang benefits of the real thing; it's best use case is at a fixed defensive position such as a gate, bastion, bridge, etc. B) it requires technical savvy to put together, it's not a zip gun; C) it requires fancy materials and/or parts - without fancy parts it will require REALLY good machining skills and access to a well-equipped machine shop; D) the ammo is expensive. I'm trying to figure out how to get it below $5 a round. O_O

[noises off: wealthy .50 BMG fanboys cheering]

 So, it's an air rifle.  It runs on CO2, straight from the bottle, around 800-900 PSI.  Oh yeah, it takes a shit if the bottle gets cold, so you have to keep the bottle warm.  And the bottle gets cold when you fire it, so you need a bigger bottle.  Did I CLAIM this was a practical idea?

 The barrel will need to be 5 feet or longer.  Longer barrel - higher muzzle velocity, and this thing is all about muzzle velocity.  The bore is considerably larger than the ammo because discarding sabot made from material-to-be-determined, probably some kind of plastic foam, very likely HDPE packaging foam.

 The ammo is fin-stabilized (COTS* model rocketry fins of carbon fiber, epoxied on) ferrocerium rods.

 Pyro Doge say, "Very sectional density.  Wow.  Much pyrophoric.  So fierce." O_O

 Get the velocity high enough and this thing absolutely will defeat light armor and set fire to every damned thing on the other side. (keep in mind even dead flashlight batteries at 400 FPS will go right through a car door, right through both sides of a steel refrigerator.  I've done it.  That was from an eight foot long device, coaxial plenum, about 1.5" bore, 100 PSI, using a sprinkler valve.

 The present proposal has orders of magnitude higher kinetic energy and sectional density than the battery gun, plus fantastic incendiary effects. 

 Valve to be determined.  There are no good off-the-shelf fast-acting valves which offer high flow rates when open, but will hold off 1,000 PSI or so.  There is a COTS solenoid valve which might serve, which is intended for hot water duty (not guaranteed to be gas-tight) in pressure washing systems.  If we can't find an off the shelf valve, a fancy fast-opening, pilot-operated valve could be manufactured in the shop.  There is an easy design with one major failing: it operates fast and hard and generally requires extra features and engineering to keep it from damaging itself.

 We need tubing - say, pipe - from the world of "Schedule 80" - pipe intended for steam and other very high pressure gases.  Bring money.  Bring a big truck too, cuz that shit ain't light.  I built a very small armature injector for my railgun project using the aforementioned solenoid valve and a small amount of Sch. 80 pipe fittings and the whole assembly weighed around thirty pounds.  Without any railgun attached to it.

 I say again: making one of these systems - maybe even fabricating the ammo - would probably break multiple national laws in many different countries, and will certainly "frighten the (LEO) horses" so to speak in your local neck of the woods. 

Kids, don't try this at home.

Unless the shit hits the fan.

 

EDIT: PS: the patents are chock-a-block full of various uses of pyrophoric metals in ammunition, but I couldn't find one damned thing about anybody making the entire ammo of a APFSDS rod type round from solid pyrophoric alloy.  Also: the stuff is prety frangible.  It can't be made "tough"so it will never defeat any sort of real, hard armor,  no matter how fast you throw it at someone.

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*COTS = Commercial Off-The-Shelf