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"If you're going to be crazy, you have to get paid for it, or else you're going to be locked up." Dr. Hunter S. Thompson

Saturday, June 19, 2021

Sgt's Time Saturday: Fuses

Greetings Me Droogs N Droogettes!
So, I've been behind Ye Olde Power Curve on doing 'instructionals' as of late.  Primarily because I started to run out of stuff I can go over in my areas of expertise.  My main thing(s) are mostly weapons related.  Also I can dig a fighting position, and maneuver myself and maybe a squad worth of people and some other helpful things... Master of None, Jack of All as a modern Infantryman should be.  

Last night though I was fucking around and it hit me.  I was measuring, cutting and testing various lengths of fuse for my 37mm "flare launcher" for some aerials, when I realized that this'd be a good Sergeants Time Saturday subject.  I load my own stuff for the launcher as material to do so is faaar cheaper than over the counter pre-loads.  A 37mm bird bomb goes for about $12-15 WITHOUT the hazmat shipping fee, and they DON'T sell them one at a time... so to continue...

SAETY WARNING: FAAFO. Playing with explosives is dangerous.  Nothin' written here is on me.
So, as I was sayin'

Visco Fuse is the most common easy-to-buy without special permits "fireworks" grade fuses.  As a kid, most of us played with "M-80s" and remember the green waterproof fuse sticking out of the thing.
THEORETICALLY they were a quarter stick of dynamite.  Outlawed in 1966, they did have one hell  of a Ka-BOOM! when we had them as a kid.  I remember DeadDad buying some, and man, those that he got blew a memorable crater in the back yard on the 4th one year.  So, enough on the firework, lets get to the initiator.

Fuse is part of the initiator, as it helps initiates the BOOM.  Other initiator include blasting caps and electric fuses, none of which I'm hitting today.  Only thing I'll say about Blasting Caps is DON'T. Unless you've been properly trained in fucking around with them, do. not. fuck. with. blasting. caps.  You'll be less apt to lose body parts that way.  The guy who trained me had 30 years experience, and was missing his pinkie and ring finger on on hand.  That ought to tell you something... so to continue.

Most common fuse out there is called Visco.  It's commonly green, waterproof, and is used primarily as a fuse for most common fireworks.  
It's core is black powder, and has various burn rates depending on a couple of things.  Manufacturer Quality has a lot to do with the burn times.  US made visco tends to be a bit more 'accurate' than the Chinese made stuff, for the values of accuracy, but is harder to find, especially these days.  This's why I was measuring, cutting and testing my cut sections.

ALWAYS test your fuse.  DO NOT count on it to be accurate 'because that's what the manufacturer said it was!' because THAT is a sure fire way to get blow'd the fuck up.

The visco comes in various colors.
Colors usually indicate what kind of fuse it is.  The most common is green visco.  It tends to be a slow burning, waterproof fuse with an average burn rate anywhere between 22-24 seconds per foot of fuse.  This's why you test it because in 'real time BOOM times' a 1 to 2 second delay OR worse, early initiation can mean death and or dismemberment.  There are three external layers to visco fuse. First, a layer of string is wound around the core, then a second, less tight, layer of string is wound in the opposite direction to prevent unraveling. The last layer is a low-nitrate nitrocellulose lacquer that keeps the fuse from falling apart. The last layer helps to make the visco fuse water resistant and to prevent moisture from degrading the black powder core.

Other 'flavors' of visco are as follows, with the approximate times of burn.

"Green" Visco Safety Fuse Speed: 23-24 sec/ft.

"White" Quick Fuse Speed: 0.1-0.4 sec/ft.

"Yellow" Fast Artillery Fuse Speed: 4-5 sec/ft

"Pink" Perfect, Medium Speed Fuse Speed: 9.5-10 sec/ft.

"Purple" Medium Artillery Fuse Speed: 4.5-5 sec/ft.

"Dark Green" Fat Cake Fuse Speed: 12-15 sec/ft.

"Light Green" Small Cannon Fuse (2mm) Speed: 24.5-25 sec/ft.

They usually come in rolls of twenty feet to a roll.  Industry standards are where I grabbed the list above BUT as I said, measure measure measure, cut once, test twice.  I was taught the 3-1-2 method. 
Best safety practices Aye?
As you can see, this 'fast' fuse is labeled 4-5 seconds per foot whereas the green is 20-24 seconds per foot.  Serious difference there Aye?  This's part of why I'm writing this one up, as where in a fucked situation, you come across a box of Pyro, best you know what you're maybe dealing with, rather than fucking around and finding out the hard way.

Now the fastest stuff is the white fuse.  a tenth-of-a-second to a half-a-second per foot.
This stuff is usually used inside a large firework to set off the secondary stuff.  Sort of like in the big aerial shots, you get  the initial Ka-Boom, followed by the pretty and Louder flares and Ka-booms...  It can also be used to assist with igniting multiple fireworks simultaneously.

Daisy Chaining as it were.  YMMV, I take no responsibility for this if you blow yourself the fuck up.

This's for intellectual exercise only dig?
So... There ya have it.  A solid rundown.  As far as finding this stuff, well, it too is currently in short supply.  Dunno why?  Makes you think that there's a conspiracy out there to keep boom-boom out of the hands of civvies Aye?

And Happy Juneteenth y'all.
So, More Later I Remain The Intrepid Reporter
Big Country


  1. Wish I had some of the M700 Time Fuse I used to work with manufacturing and testing M81 Igniters. Was using fuse from the official supplier for testing on a contract. Still the fuse had inconsistent burn times, even within the same roll. So Big Country is not kidding about checking burn times. The shock tube was really fun too. Talk about instantaneous!

  2. Early in my life i had a summer job working on a fireworks crew. These are the ones who set off public display using big fireworks not the stuff from corner gas stores.

    Digging holes for the mortar tubes was never the fun part.
    I started out as a runner. Thats the guy who runs mortar rounds from the rearward storage to the forward loading ready pile. In case of sparks blowing back you don't keep a bunch of rounds up close. A runner is assigned to a specific diameter of rounds to prevent someone putting the wrong round in the wrong pile.

    Then i was a swabber, thats the guy who uses a long stick with spikes to reach into a tube and pull out any remaining flaming debris. You get 2 rows of tubes to watch. When they fire you watch to make sure they all launched, swabbing a habgfire is dangerous.

    Then i was a loader, you take the ready rounds and load them in the tubes moving from the front to the back removing the paper covers from the end of the fuse.

    My last summer doing that job i got to be a lighter and actually light off rounds. Being tge youngest i usually got the 3in or 4in rows, but show i got assigned the 3in and the two 8in tubes that were preloaded for the finally.

    Ours were supposed to be about 20ish seconds per fuse. That meant if you were slow the front round of your bank of 4 or 5 tubes would be going off before you had the last obe lit.

    Occassionally the fuse burned much faster. Light a 3in and started to turn and off it went.

    I'm pretty sure the intervening years and all the rules about children has made it unlikely a teen would be allowed to do that job again.


  3. Don't think temp and humidity don't change the burn-rate, either.

    From hot, dry afternoon to cool, moist morning, time fuse will slow by up to 4 seconds.

    At least, that's the way M700 worked for me at the Kahuku and Wainaie training aeeas by the ocean.

    Knowing the fuse is when you can do a one-foot test burn, calculate a humidity factor, cut it to length in the evening and it goes off on-time so you can get a bit of extra shut-eye the morning you have to use it.

    Should pick up some fuse to get back in practice, heard they use it in Minecraft.

    1. That's where we got our det at Pupukea Boy Scout Camp. Good times. My brother still has a burn scar on his quadricep.

  4. 70/30 mix of potassium perchlorate and big number mesh powdered dark aluminum makes the guts of the M-series and 'quarter sticks'. Commonly called 'flash' powder, it's the bright white flash in fireworks. Anti-static spray is your friend, and mixed gently in a ziplock bag with gloves and a face shield IN SMALL QUANTITIES. You'll lose fingers with anything more than a few grams of this stuff, and it takes a static spark to set it off. Do not compress it, light and airy is your friend with the 'flash'.
    The last one I built a few weeks ago was 7.5oz, and leveled out to 3' in diameter a 12" deep hole in the dirt. The normal ladyfinger style is milligrams size, usually 50mg or less. A 'true' but illegal M-80 is in the 3 gram range, a 'quarter stick' in the X times that range, but usually well under 50g. That 7.5oz was over 200 grams.

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