Wednesday, October 29, 2014

$15 Homemade Curved Pistol Plate - that actually works!

This is a composite armor insert I built at home with hardware store materials.  It successfully stopped 10 shots of 9x19mm FMJ fired from about 15 feet away. It cost $15 in materials to build.

For video of the test see:

The materials used to make this are porcelain tiles, and layers of fiberglass fabrics, all laminated together with polyester resin. It was clamped in a wooden mold during curing to give it the desired curved shape.  The armor is curved to make it comfortable to wear against the chest or back. It is designed to fit into a fabric armor or plate carrier which are commercially available and inexpensive.

The armor traps and absorbs the bullets to prevent any fragmentation from injuring the wearer. There is some mild back face deformation on the armor where the 9mm bullets have struck. The bulges are less than 1/2" tall.

After the armor passed the test successfully, I shot it with an AK47 (7.62x39mm) to see what would happen. The bullets zipped through as expected, and the resulting blowout can be seen above on the back of the armor.

The armor materials are layered in this order, from the front (strike face) to the back (wear face):

1 layer 18oz/yard Woven Roving Fiberglass cloth - fragmentation/retention liner
1 layer of 2x2 porcelain tiles - bullet fracture layer
10 layers 18oz /yard Woven Roving Fiberglass cloth - spall liner

The layers are saturated with polyester resin and clamped in a mold to cure. The resulting armor is spray painted black and is ready for use.

Tuesday, August 05, 2014

DIY 12 Gauge Bandolier

Since my pipe shotgun has no magazine, I decided to make a bandolier to go along with it. I did not want it to be very heavy or carry many rounds. Most bandoliers are made from nylon webbing with stretch fabric loops, and the rounds are situated very closely together. I've used these before and I'm not a big fan of them. The fabric can lose its stretchiness over time, its cumbersome to reload the loops, and the rounds are so close together that it can be difficult to grab a single round. Another commercial option is shell pouches, or a side saddle that mounts to the gun. But I felt like making something out of scraps I had flying around.

I made a simple bandolier using two layers of nylon webbing I had saved from some old duffel bag carrying strap. The loops are short sections of 3/4" PVC pipe that a 12 gauge shotgun shell fits snugly into up to the brass. The back webbing lays flat and the other piece goes over the PVC sections. The PVC  and nylon webbing are glued together with clear silicon caulking. I have 10 loops on this bandolier so can carry 10 rounds.

To make this I started by cutting the sections off of the 3/4" pipe that are the same length as the nylon webbing width. The webbing I had was 1.5" wide.

Once the first is cut I use it as a template on the PVC pipe to mark each successive cut. I used a miter saw to cut the sections. I don't actually have a miter box anymore, just the saw. I held the PVC pipe in my vise to keep it secure. 

Once the ten pieces were cut, I put a piece of 80 grit sandpaper on my bench top and rubbed the cutoff sections to get rid of the plastic burrs and rough spots. This was somewhat effective to clean them up but I think a dedicated PVC deburring tool would have worked much better. If I were doing much more than 10 loops, It might have been worth it to get one.

To clean up the burrs on the inside edge I ran a box cutter blade around the inside rim at a 45 degree angle.  The little curl of plastic came off in one ribbon.

After they were smoothed I layed one piece of the nylon webbing out and glued each pvc section to it with a single bead of silicon caulking. I rubbed each peice around a little to ensure the silicon was embedded well into the nylon webbing. I spaced them out fairly widely since I only had 10. I let this cure overnight. The next step was to add the top nylon webbing to secure the loops. I put several beads on each PVC section and on the nylon backstrap. I pressed everything down into place. I was worried that I would need to use clamps but the silicon is viscous enough that it held everything generally in place. Again, I let this cure overnight.You can see some of the silicon at the junction of the two straps here:

The final step was to trim everything to length. Nylon webbing can be cut with ordinary scissors. It can start to fray once cut but this is easily rectified by fusing the cut ends with a match flame. I cut the bandolier to length with some overlap. I used a plastic strap adjuster to make the bandolier into a loop - this can be tightened or loosened as needed.It needs to be run through the adjuster twice to stay firmly in place.

Tested it out and it looks like it will work well. Not bad for a few dollars in materials.

To adjust how tightly the shells fit, one can place a small piece of scotch tape on the inside of each PVC piece, or lightly sand the inside of the peices with some sandpaper wrapped around a finger.

Sunday, August 03, 2014

Homemade 12 Gauge Pipe Shotgun

This shotgun is a one of the simplest firearms that can be built. That said, this is for educational purposes only. Do not attempt to build this gun! The materials and ammunition are cheap and commonly available, and it can be made quickly with a minimum of tools.

Here is a live demo of it in action:

This firearm design was inspired by the infamous 4-winds shotgun and the Philippine guerrilla gun.

It utilizes the so-called "slam-bang", or blow forward, action. To fire, a 12 gauge shotgun shell is placed into the barrel, which is then slid into the receiver, and slammed rearward. A nail crushes the primer in the process. After firing, the barrel is removed, and the spent shell pulled out by hand.

It is made from two pieces of steel plumbing pipe and an endcap: one pipe acts as the barrel, the other, larger diameter pipe and endcap as a receiver. A small piece of wooden dowel and a nail make up the hammer and firing pin. The stock is made from a length of ordinary 2x6 lumber (I think this is probably spruce).

To comply with US Federal Title 1 requirements: It has a barrel length of 19" (18" federal minimum) and an overall length of 35" (26" federal minimum).

The Receiver

The body of the receiver is made from a 1" diameter, 6" long, schedule 40 galvanized pipe nipple. This comes threaded on both ends.  I cut off the threaded section on one end, this will be the front of the receiver that accepts the barrel. The threads on the other end will be used to attach a 1" pipe cap later. Two holes are drilled and tapped on the bottom to attach to the stock, and a hole is drilled and tapped on the side to provide the barrel lock/safety bolt.

The most critical task for building the receiver is that the barrel freely slides all the way inside of it without sticking or binding. As purchased the two will not likely fit do to manufacturing tolerances and imperfections - the dimensions are very close. Either the barrel outside can be made smaller via grinding or sanding, or the receiver inside can be made bigger via sanding. Or, some combination of both.This is what I did.

One trick is to find a 1" pipe nipple that has no internal weld seam. Plumbing pipe of this kind is made by bending a flat piece of steel over a cylindrical mandrel and welding the two ends together to form the finished pipe. This creates a weld seam that is invisible on the outside but usually very obvious on the inside. This seam sticks out and interferes with the barrel's insertion. I have discovered that some pipe nipples have this weld bead ground off already inside, and some do not. It is possible to remove this seam oneself but it is time and labor intensive, and requires making a tool. The tool is a wooden dowel with coarse sandpaper glued to the outside.

It is much easier to slightly reduce the diameter of the barrel since it can be reached with tools. However care must be take not to make it too thin. This is covered below in the barrel section.

The Hammer/Firing Pin
The hammer is fixed at the rear of the receiver and relies on the barrel to bring the shell to it. It consist of a 1" diameter oak dowel that is cut to 1/2" in length. The firing pin is made from a roofing nail that is cut to 5/8" long with hacksaw. The tip of the nail is rounded over with a file to give a blunt profile. It is important not to use a sharp tip as it may pierce the primer instead of crushing it. A hole is drilled through the center of the dowel using a drill bit the same size as the roofing nail. Lastly, a piece of cardboard is cut to 1/8" larger in all directions than the oak dowel - this serves to keep the hammer and firing pin secure at the end of the receiver.

To assemble, the nail is punched through the center of the cardboard piece and fed through the hole in the dowel. The tip of the nail should slightly protrude above the dowel.

Then the hammer/firing pin are placed into the threaded endcap. The cardboard piece sticks into the threads of the end cap, preventing the hammer from falling out.

If if needs to be removed for replacement or cleaning a pair of needle-nose pliers works fine.

The Barrel

The barrel is a 19 inch long peice of 3/4-inch schedule 40 galvanized steel pipe. Black pipe could also be used here. If the steel pipe has threads they should be cut off on the breech side otherwise the chamber will be weak. This can be accomplished with a hacksaw. The barrel should not be shorter than 18" to comply with US federal legal requirements. 18.5" is a good minimum to observe. I made sure to square off the chamber end with a file so the lip of the shotgun shell would rest on the edge snugly.

I made a slant compensator in the barrel by cutting the muzzle at a 45 degree angle with a hacksaw, then cleaning the cut up with a file. This in theory will reduce muzzle flip. An optional front bead sight was also made using a machine screw to give something to aim with.  I drilled a hole and tapped for the threads, in this case 10-32.  The screw is ground on the bottom to prevent it from protruding into and potentially obstructing the barrel, a dangerous condition for any firearm.

I polished/sanded the barrel near the breach end with a flap disk on a grinder until it slid easily into the receiver without sticking or binding. The trick here was to keep the grinder moving up and down the barrel and never remaining on one spot as you slowly move around the barrel. 

I went very easy on the barrel, taking off a very small amount of material all the way around. Shotgun shells operate at relatively low pressure as far as firearms go. But his pipe is not rated for this kind of application. This design however sleeves barrel in another steel pipe during firing to give a some measure of safety.

Making the Stock

I made a basic stock design in MS Paint, scaled it up, and printed on two sheets of paper. This can all be done in the program itself. I then glued the sheets to a piece of cardboard and cut out them out. This created a template for tracing onto the 2x6. I found the stock a tad short and thin for my liking so I slightly changed the dimensions as I traced it to make everything bigger and longer.

The stock is cut out using a panel saw a section at the time. I shaped the edge of the stock using a router with a round-over bit. This could also be accomplished with 60 or 80 grit sandpaper, but much more slowly.

The stock is inlet for the receiver using a hole saw that is slightly smaller than the receiver. The next step was to wrap some sandpaper around the receiver and use it as a sanding block to bring the bed to correct size. I had to be careful to prevent the edges of the inlet area from cracking.

Once complete, I lined the bed of the receiver with some fiberglass tape and wood glue to reinforce the relatively fragile edges. The receiver was wrapped in aluminum foil as a release and clamped down onto the glue. If I were to do it again, I would used epoxy here instead. The glue isn't really ideal for bedding a stock (too soft), but it works well enough in a pinch.

3/8" holes are drilled to accommodate the two 3/8 bolts which will hold the receiver to the stock. These bolts are way overkill but they are what I had flying around. Much smaller bolts could be used. The stock has a wooden block in front of the endcap to provide some measure of safety to the user in the event the receiver end threads should fail - the end cap would not be blown directly into the user's face.  This will be later reinforced with screws as it is not very strong - the grain of the wood runs front to back.

The bottom of the holes are counterbored with a big drill bit to recess the bolt heads. They must be tightened with a socket wrench.

The receiver was previously drilled and threads tapped in the holes. The bolts only engage the threads for the thickness of the receiver(maybe 1/8"), as the barrel needs to freely slide past them. 

A few washers were added under the bolt heads to get the bolts to tighten up without going too far into the receiver and blocking the movement of the barrel.

The receiver was then removed from the stock, and sanded lightly by hand. Two coats of gunstock stain are wiped on with a rag, with 4 hours between the coats.

Then three coats of polyurethane are applied with a very light scuff sanding between coats. 400 grit sandpaper was used and very little pressure was applied. A sanding block is used to keep from sanding through each coat.

A rag was used to apply the poly. Several companies make "wipe on poly" specifically but the regular stuff worked just fine. At least 4 hours were given between the coats, and a fan was used to speed drying.

The finishing touch on the stock is the recoil pad to making shooting more comfortable. The recoil pad is made from a $2 pair of black walmart flip flops.

I placed the butt of the stock on the flip flop and traced with a permanent marker. I cut it slightly larger using a pair of scissors.

Next step was to drill some shallow holes in the buttstock to provide a good surface for gluing. Gluing to end-grain does not work well otherwise.

Then I ran aluminum tape around the butt-stock to prevent glue from getting on the finish, and to protect it from sanding of the pad later. I mixed some 5-minute epoxy, slathered it onto the stock, and pressed the recoil pad into place. I used some masking tape to hold tight while it cures. 

After the epoxy cured, I sanded the foam with 60-grit sandpaper to get the desired rounded over shape. I also masked off the pad and stock afterwards and painted a 1/4" black band next to the pad.

This band helps hide my less than stellar sanding job on the pad/stock interface that exposed the raw wood. This would probably be less of a problem if I attached and sanded the pad *before* finishing the stock.

Final Assembly

The shotgun is assembled as shown:

The receiver is attached to the stock with the bolts, the endcap screwed and tightened onto the receiver end. The final step is to insert the barrel, and mark through the receiver bolt stop hole with a permanent marker, and then make a divot in the barrel using a drill. This divot allows the barrel to be securely "locked" when the bolt is screwed in. This is important as the barrel would otherwise fall out of the gun when carried.

I made a divot with the barrel fully pressed against the endcap, and then moved it forward half an inch for another divot. This way I can secure the barrel fully rearward (chamber empty), and forward slightly (shell chambered). This functions as somewhat of "safety" though should not really be relied on as such. 

One optional but pretty useful feature would be a forward grip that attaches to the barrel. This would make it easier to slide it rearward and to hold the barrel when removing/inserting a shotgun shell. I may put one on in the future.

Thursday, December 19, 2013

Homemade Bulletproof Armor - Ceramic / Fiberglass Shard

This armor is a ceramic-fiberglass composite constructed from an ordinary bathroom tile and fiberglass woven roving which are glued together with polyester resin. Either porcelain or ordinary ceramic tile can be used.  Check out the video here:

The basic design is to encapsulate the tile in a sheet of fiberglass and resin, where there is at least one layer on the threat side to keep it held together and control fragmentation, and many more layers on the back side to capture and prevent spall. The idea is that the hard tile will fracture or blunt the incoming bullet so it can be stopped with fewer layers of fiberglass than an armor that is made from only fiberglass.

The fiberglass fabric is cut to the right size with a sharp box-cutter blade, the tile centered on the ply, and the excess material is folded around the back. This gives 1 layer of fiberglass on the front, and 8 layers on the back due to the folds. This will thicken the tile by about 1/8th of an inch. The shard is saturated with resin and clamped between two wood sheets using saran wrap as a mold release.

An additional armor shard was constructed with two sheets of woven roving which gives 2 fragmentation layers on the front and 16 spall layers on the back. This was done to provide another test piece in case the first armor piece failed to stop the bullet.

The armor pieces can be any size, which is dictated by the size of the tile used. The two armor pieces were created with a tile that 4.25" square. The armor "shards" can either be incorporated into a larger solid panel, or perhaps used individually in an overlapping configuration to create a flexible vest. Either way they are easy to construct and test in bulk without using much material.

Test Results and Analysis:

The first armor tile with 1x8 layers successfully stopped a single 9mm FMJ bullet fired from a pistol-length barrel. The second piece also stopped 9mm without any issues. Therefore it was determined that a single ply of WR is all that is needed to make this armor stop one round of 9mm FMJ. Multiple shots to the same piece were not tested.

The video of the test is here:

The 1x8 tile below with the bullet fragments extracted from the front using a pair of needle nose pliers. The full metal jacket bullet was completely mushroomed and broke into multiple fragments within the tile itself - I didn't find any evidence that the fragments even reached the spall liner.

There were numerous granules of the ceramic tile in the impact crater as well. The combination of the bullet and armor fragments (spall), and have been easily caught by the layers of woven roving on the back of the tile.

It would be interesting to see what additional pistol bullets that this armor could stop.

Sunday, March 03, 2013

DIY 110 V Portable Arc Welder - with DC!

I needed a more portable arc welder so I built this unit 110 V unit that weighs 40 lbs. It is made entirely of scrap parts. The frame is wood, the welding and power cables are from appliances, and the transformers/wiring are from microwaves ovens.

It is made form 3./4" plywood scraps. It uses a piece of EMT tubing as a handle. It is easy to pick up with one hand to tote around. I can not say the same for my other welder.



The unit has infinite welding current control and can do around 60 amps max. It uses a massive light dimmer type circuit to control the welding current. The circuit controls a triac which varies the input power to the transformers.


The transformer primaries are put in parallel so both are energized with 110 volt. If welding too long at max power it will pop the breaker on a 20 amp circuit. Running slightly lower output works great. The transformer secondaries have been cut off and rewound with 12 gauge copper wire, and then put in series to generate approximately 50 volts AC. This then goes to the bridge rectifier.

 The bridge rectifier is rated at 60 amps and converts the AC to DC, multiplying it up to 75 VDC open circuit, which goes to the filter choke. Another microwave transformer core that was completely rewound with 12 gauge wire (50 turns) serves as the choke to smooth the welding current before it goes to the electrode.

The ground clamp is a battery charging alligator clip. The rod holder or "stinger" is a standard model that cost $10.  The ground and electrode welding cables are made from 3-conductor, 12-gauge appliance cables with the conductors in parallel to give 60 amps + capability and minimize voltage drop. Also this makes the cables very flexible.

I was able to weld with 1/8" rod without trouble, you can see my first test bead above. Both 1/16" and 3/32 rods also would work. Due to the high OCV of the welder, I am able to start the arc very easily.