Science/Engineering/Technical forums

All work and no play...oh, wait, that's not me at all!
This was also an excuse to fiddle with the new computer and video editing. I'm learning, which is often fun.

DaveK (chemist, firearm instructor, Renaissance man) and I have been messing around with some more-sensitive reactive targets for the range.
The idea is to get them sensitive enough to go with a .22lr, a .177 pellet gun, or maybe even an airsoft pellet.
We clearly have the sensitive part - we need to do work on the safety. These are NICE.

Here is documentation on an early attempt. These have "issues" and fall squarely into the "don't try this at home" category for now.
Chlorate/Sulfur mixes are known to "go" spontaneously, and are in general touchy even if they don't. Here, I am not adding the safety-enhancing calcium carbonate, as this set of tests is mix and go.
Sandblasting sand is added to the mix and greatly enhances shock sensitivity. It was needed to get reliable detonation in the hammer drop test (see, Tenney Davis, Chemistry of powder and explosives), but may not be needed for projectiles- another test to do.
Problems were experienced with mixture separation. Just carrying a little pouch of this stuff down range would allow settling. It needs a binder and granulation to prevent that, and
it could be a little less sensitive as a result and still be fine for this use. More work needs to be done, this is phase 1.

Here is video of a couple of tests. The first shot is of a mix with added Mg, but less total fuel than ideal. Some Mg was lost - a slip between the cup and the lip, it tends to float above the rest of the mix as what I have is thin chips from turnings I got in a fire starting kit. Shot with a .22lr.
The second shot is a few more grams of a chemically correct mix, and was shot with a pellet rifle. Range around 30 yards in both cases. Going out on a limb, since this IS legal, here it is as a private video on youtube. I'm just trying to avoid educating the teeny-bombers here.
https://youtu.be/jmhQBJ5DaS0

Yes, we all have to jump through some hoops with things like this in today's world. The zip is because the board won't allow mp4,
and because this doesn't want to be out there for any idiot - lets at least make it so you have to know a little.

Safety notes - pay attention and keep your fingers and ears!

Chlorate and sulfur mixes have some issues, and are deprecated in pyrotechnics. Potassium chlorate slowly decomposes and gives off a little nascent oxygen.
In the presence of any moisture, Sulfer combines with this super reactive O to make sulfurous and sulfuric acid. This catalyzes further decomposition of
the potassium chlorate, and it's exothermic. Boom. Calcium carbonate added to the mix (omitted here) helps prevent this, but nothing is perfect.
We are looking at other compositions for this reason.

If you must grind a chlorate, do it in a perfectly clean mortar/pestle, as the slightest hint of any fuel will cause a small explosion which will at minimum
ruin your underwear, and likely break your mortar. I had to grind mine a little as it's been on the shelf for years and had gotten lumpy.

If you test this mix on an anvil with a hammer - it doesn't take a serious blow - USE HEARING PROTECTION. Even a couple of matcheads worth of this
will do permanent damage. I'm reminded of similar amounts of mercury fulminate. The little rocks (the sandblasting 40 grit obsidian) come out fast enough
to penetrate unprotected skin as well - guess how I know.

Doug
ammonium nitrate and Aluminium powder is also great (Ammonal)
half a teaspoon on an anvil hit with hammer results in hammer handle and no head
Stanley 40 oz steel shafted hammer

Sounds like Tannerite. The aluminum (sorry, I refuse to use British when American English works ) must be extremely finely sieved.

I haven't done any tests on tannerite or the homebrew version as to sensitivity lately, but a selling point is that it WON'T go from a hammer blow. They even produced a video showing all the ways it would not detonate. Now, that was surely partly sales and government avoidance stuff... but here, the normal prilled AN + dark pyro (super fine Al) doesn't go with ahammer, and won't go with a pistol bullet at all - needs 2k+ FPS to work (and then, yes, it's great). Maybe powdering the AN helps that. We did do tests that day with both super dry fresh AN, and some that'd been around awhile and had absorbed around 3% water.
Both worked. The wet version a little better - perhaps the vaporized water added to the total gas produced. Detonation isn't the same thing as deflagration!

A slightly boosted version is shown here, hit by a 3300 fps bullet from my record setting benchrest rifle. It's really good. Sorry bout the zipped videos, not sure how I can put this up on youtube without getting the wrong kind of attention.
Kind of the end of testing for that day by ruining the barrel we were using to hold targets just then.
Let's try private on youtube.
https://youtu.be/0Aq_ywD99iw



But what we're working on just now is something that Dave can use with his grandkids in suburbia with a pellet rifle (~ 1k fps on a good day, light pellet), which doesn't make enough noise to anger the neighbors. He lives in a place where discharging a firearm is illegal... most built up areas are like that in the US. I am lucky (by design) that I live in an area where the only rule is "don't anger the other taxpayers" and here, we're all friends. No Karens in my 'hood.

My thinking, since my situation is almost the opposite (a mere 12 miles away) - is to create a modular system that can serve his needs, and my wants.
I'm thinking of stackable disks - say about the size of a silver dollar, maybe a little thicker. One would be this class of stuff - easy to initiate with even a plastic air-gun bullet (airsoft). But you could then stack others behind that to provide fancy pyrotechinc effects, or a real good boom - that's where the AN mixes come in, lots of heave, though not much brisance (they have slow risetime).
The one I show above has perchlorate in it too and is about twice as effective in producing shock and really using all the material before disruption compared to Tannerite.

It's all a work in progress, and developed as a side issue for something to do when we old farts have finished eating our monthly sushi picnic.

Very nice. I can set off regular Tannerite with a single-shot .22 bolter. Just use .22 airgun pellets and a green shot for Ramset guns. Never chronographed it, but the pellet hits before you hear the crack. Easily more than 2200 fps.

I sort of don't want to do it with a gold shot...

Speed* does it, or as a British patent for exploding targets Dave found mentions - a bit of an anvil behind the compound helps by giving the system something to crush against, and need not be much.

However, here a main goal is to create something Dave can use legally in the town he lives in, with his grandkids. So, no firearm - totally illegal in city limits - and no boom - neighbors. So we're working on a sensitive pyro display that at least gives light and smoke...It's not like we don't have some serious guns, you understand...but there are times and places.

* Actually, a quick risetime of pressure, which becomes heat, does it. That's why adding a bit of grit helps, as the pointy contacts increase the force at the points for a given bulk effective psi created by bullet impact and the inertia of the compound.
In hammer/anvil tests, it's a huge effect on sensitivity. Seems to translate to target reality as well. But that's why we test, despite how painful it is...(nope, actually it's great fun!)

Bill sends this along. Dave "evidence that politics can turn a man into a pathetic wimp!".
Me - someone thought guns were quiet, like on TV? Talk about low-information. People with no experience of reality want to tell us how to live - and how to think? Insist they know better? That's a nope.

I thought that top half from Kuntzman had to be fake or at least edited with extra hyperbole, but no. A quick web search shows that it is extracted from a genuine investigative article he did.

Ah, but the real question, given the antics of what is loosely called journalism today, is what anonymous sources familiar with the matter told him what a cannon sounds like, and how a bazooka feels, right? Followed by how it's Trump's fault with help from the Russians, of course....

No kidding.

How many members here have been on a cannon range? Those boys are scary loud. I don't know if I've said it here or not, but I was driving north on East Range Road at Ft. Hood when the cannon crew set off a 105mm howitzer not fifty feet uphill from me. I swear my truck bounced right, but it might have been a pucker-factor that caused me to glitch the wheel. I'd swear they waited for me to go by to pull the lanyard...