Introduction: Double-Barrel Shotfun

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It was just a spelling mistake in a humorous sub-thread, but it eventually became...

The Double-Barrel Shotfun - dealing out enjoyment at the pull of a trigger!

It's just what you needed - an overly-complex method of firing off two party-poppers at once.

(You can now accessorise your Shotfun with a dedicated bandolier!)

Step 1: Materials and Tools

You can modify this project to your needs, but this is what I used:
  • 4mm plywood sheet
  • Offcut of 6mm plywood
  • 32mm waste pipe
  • Industrial adhesive
  • Masking tape
  • 6mm dowel
  • Scrap corrugated card
The tool list is flexible - I used a laser cutter, but only because I could.  Similar results could be achieved with skilled use of traditional power and hand tools.
  • Lasercutter
  • Scrollsaw
  • Teaspoon
  • Files
  • Sander
  • Rubber mallet

Step 2: Prototyping

I first needed to prove that my idea worked.

This quick lash-up proved that a steady pull via a lever would work to fire a party popper.

Step 3: Lock, Stock...

Once the concept was proven, I needed to stream-line it. I drew the laser cutting files in LaserCAM 2D, purely because it's the software my school bought with the laser cutter.  You can reproduce your own version in whatever software you prefer.

I designed most of it to be out of 4mm ply, but I decided that the section that would brace the poppers (the part that looks a liitle bit like a heart, and a little like a Batman logo) needed to be stronger, so I cut that out of 6mm plywood.

I took a screenshot of the design that you can use - the odd layout is to fit the piece of plywood I had close to hand.

The MCM file itself is in the zip folder with this step.  It's not huge, it just isn't recognised by the uploader if you leave it as an MCM.

Step 4: Testing & Cutting

To check the parts fit together, and fit my hand, I ran off a set of pieces in corrugated cardboard.

The parts all fit perfectly, but I discovered a bug in the software; the curves of the bracing piece were only rastered (etched), not cut by the laser cutter.  I ended up using the rastered cardboard test-piece as a template for the bracing piece, which I cut out roughly with my scrollsaw, then filed and sanded it to shape.

Step 5: Construction

See the photos for laying the parts out.

I used short pieces of 6mm dowel to brace the parts.  The fit in the laser-cut holes was snug, so I used a small rubber mallet to get them in place, protecting the gun with a scrap of timber. Wood-glue between the layers ensures a permanent fix.


Watch which way round you fit the lever - the slot needs to face backwards - and be careful not to glue it in place.  It's not obvious from the images, but the hole I cut in the lever is half a millimetre wider than the other holes, so that the lever will move freely, not stiffly.

I sanded the dowels flush with the plywood, and cleaned off the cutting soot with a few strokes of the same sandpaper.

Once the rest of the woodwork was glued, I glued and friction-fitted the bracing piece in place.

Step 6: Making Barrels

I cut two pieces of waste-pipe for the barrels, each just over 40cm long.

The waste pipe I used was sold as "32mm diameter", which turned out to be the internal diameter.  This was the closest fit I could get to the 26mm outer diameter of the party poppers.

I could have bought 28mm copper tube, but it cost far, far more than the plastic waste pipe, and I'm not convinced that party poppers come in a standard diameter, so there's wiggle-room to fit larger poppers.

To be able to load the gun, I needed a notch out of the barrels.  I measured it by eye, then cut it with the scroll-saw.  The curved slot gives enough space to push the popper into the barrel, and then drop the stalk of the popper into the notch of the bracing piece.

See the photos for the size of the notch compared to the poppers.

Step 7: Fit Barrels.

With a spare set of hands (thank you, Kitewife!), I fitted the barrels in place with masking tape, and then filled in the gap between the plywood and the barrel with Sugru.

To do the full length of the barrel took two sachets of black Sugru.  I rolled the Sugru into "worms", then used the end of a teaspoon to push the worms into the gap under the barrels, and to smooth off the surface. See the Sugru packs and website for correct handling procedures.


The Sugru failed! It may have been a lack of contact area, or the age of the packs (rather close to their expiry date), but it didn't survive some basic handling, do I cleaned off the Sugru, and tried again with an interesting mastic-style industrial adhesive called Sticks like sh*t (seriously,  check the photos! ).

Step 8: Finishing

Here, I reached a dilemma...

My original intention was to paint the barrels matt-black, and use a dark varnish on the stock (to make the shotfun look more like a shotgun), but now, as I've been playing with it, the plastic-and-ply colour scheme has grown on me.  I like it, and, for now, I'm going to leave it.

Step 9: Modified Ammunition

Paper streamers are fun, but it's more fun to cover folk in flour!

Party poppers are very simple to modify, as long as you take a little care:
  1. Use a thin blade or long fingernail to prise out the cardboard disc, doing as little damage as possible.
  2. I remove the existing streamers, but you can leave them in if you want.
  3. Do not remove the second disc - I tried it, to fit in more flour, but the popper's explosive needs space to expand. If you pack things around the popping bit, nothing gets fired out.
  4. About half a teaspoon of flour fits in nicely. Don't pack it tightly, or it won't come out.
  5. Slide the original card disc back into place, between the plastic corrugations - sliding a thumbnail around the edge works well.
If you're not taking photos as you go, each popper takes less than a minute to modify.  The results are satisfying...

Step 10: Loading and Using

Before using, you need to tie knots in the strings of your party poppers.

To load, push the popper in through the notch, and lay the string through the slot in the lever.  You can load both barrels, and put both strings in the slot at the same time.

Pull the lever, and... !

I have, of course, entered this in the Epilog laser contest; if you would be so kind as to vote, though I doubt I will get to use a laser cutter very much, since both our boys want careers in design and engineering...
Epilog Challenge V

Runner Up in the
Epilog Challenge V

Halloween Props Contest

Participated in the
Halloween Props Contest