Cratermaker Shrapnel Testing

    You have probably been preached to, at some point, about the inherent dangers of shrapnel and the use of metal casings for salutes and explosives. Probably by me, and probably in reference to cratermakers. For most people, however, this is one of those nagging things they push to the back of their minds and don't immediately consider when they go out to blow things up. The shrapnel warnings get filed away in the same place in your brain as all your mother's warnings not to go swimming for an hour after you eat.
    Thus, once summer's day I set out to test and illustrate the shrapnel producing effects of a standard black powder filled cratermaker. The original exposé was posted with pictures on the Totse message boards. Since the post and pictures have thus been lost I present for your reading pleasure a more thorough and detailed analysis of the same tests.

    Shrapnel (the term coined by a civil war engineer of the same name), is the collective term for all debris propelled by the explosion of a shell, salute, or bomb. In general the term refers to fragments of metal torn from the casing of the bomb in question or pieces of metal purpose-built into it to kill or injure persons caught near the blast. In terms of military usage, shrapnel is good. It maims and kills enemies beyond the explosive radius of the bomb itself. In terms of homebrew pyrotechnics, shrapnel is bad. It tends to strike without warning and injure people a considerable distance away from the plast who would otherwise be safe.
    Shrapnel is commonly underestimated by inexperienced pyros, and as a result is one of the leading causes of injury and deaths in the field. Any bomb or salute with a hard casing is a shrapnel risk, be the casing metal, plastic, concrete, or glass. Fragments of the casing are theoretically fired away with the same velocity as the bomb explodes. It is thus preferable to take shelter from any flying fragments of things that you blow up. There is no way to truly accurately predict the path of the shrapnel from an explosion. This unpredictability is what makes shrapnel so dangerous. You may well have set of a dozen or more metal-cased explosive devices in your time and never seen a lick of the stuff. That just means you got lucky twelve times. Your thirteenth, or any other time, may well be the one time you aren't so. You have to be lucky every time but you only have to be unlucky once.
    And now for the test. My personal favorite explosive plaything is the Cratermaker. Cratermakers are empty 12 gram CO2 cartridge filled with black powder, match heads, flash powder, or similar low explosive. If you've had access to the internet and my rantings for more than five minutes you've probably already head this speil before - Repeatedly.
    Regardless, something was needed to catch the fragments resulting from the blast and record, with reasonable accuracy, the path that the fragments took. Nothing too high tech was required. In fact, this large cardboard speaker box fit the bill quite nicely.

    One standard black powder filled cratermaker was prepared and placed on the ground in the center of the box. I recorded which direction is was facing (relative to the end with the fuse in it). After measuring everything out and snapping a quick photo the fuse was lit and I vacated the premises.
    And yea, verily did the box explode. And thusly were the scattered pieces collected.
    The box parts clearly displayed several puncture marks from the cratermaker's shrapnel. I took the box home and pieced it back together. Using the starting position of the cratermaker itself inside the box I was able to calculate the paths the pieces of shrapnel took as they flew from the blast site. I came up with this:
    The short green line indicates the direction the fuse of the cratermaker was pointing. There were six recorded fragments that left the blast site. The four in green were recovered, at length. The fragment represented by the blue line rocketed off into the bushes and left no evidence of itself other than a hole punched in the box. The fragment in red, however, clearly illustrated the dangers of shrapnel.
    For here it is, buried some three quarers of an inch into a hardwood log not far from the blast site. Had this fragment struck flesh it easily would have punctured a leg or an arm and passed clean through it. A chest hit would likely involve serious organ damage, and a head hit probably would have been fatal. This, kids, is why you take cover from shrapnel. Not because it could hurt you or take out an eye - Because it can easily kill you.
    The rest of the recovered fragments are varied. Some are large, some are small, some are pointy, some are rounded. All of them would have posed serious risk to anyone in their path.

    The trouble with cratermakers is that their shrapnel output varies. In general weaker and slower burning explosives (match heads, smokeless powder) tend to split the cartridge and not fragment it. Black powder is a mixed bag and sometimes splits, sometimes fragments, and sometimes does a little of both. Very high velocity explosives like flash powder and acetone peroxide almost invariably shatter the cratermaker's casing into ten or twenty shards. All of this, though, is variable. I've seen match heads frag a CO2 cartridge like a hand grenade and I've seen flash filled cratermakers peel themselves open like flowers. It's simply not something that you can predict.
    Now you have all the scary facts about how dangerous shrapnel is; Here is what to do about it: When in doubt, take cover. In the case of a shrapnel producing device, always put something strong enough to withstand the impact of the resulting fragments between you and the bomb. Suitable pieces of scenery include trees, brick or cement walls, boulders, and moderately sized mounds of earth. If you are building your own blast site a piece of 3/4 inch thick plywood should be sufficient to stop shrapnel from any low explosive device. Always remember the cardinal rule: Shrapnel's flight is line-of-sight. If you can see it, it can kill you.

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