Protecting Electronics in Metal Military Surplus Ammunition Cans- Part 1, by J.T.

In this multi-part article, I am sharing a better solution for protecting sensitive electronics stored in metal military surplus ammunition cans. There are many references for making a Faraday Cage on SurvivalBlog. Some references go back as far as 2005. One solution was proposed in 2006 that required the removal of the rubber gasket on ammo cans and replacing the seals with a conductive material (stainless steel or steel wool). Other articles suggested the use of a galvanized garbage can that is sealed up with conductive metallic tape, or an open head steel drum, or using an old microwave oven and a metal cabinet. I have read and researched many great comments and feedback on the effectiveness of these EMP protection measures.

Previous Proposals

All of the proposed solutions are more or less effective. Some have been tested using some sophisticated test equipment that gives you some confidence that different approaches will be effective. But unless your solution is tested, then it’s still unclear if or how effective your solution will be when needed in the future.

The problem with many of these solutions is that each didn’t make it convenient to access. Perhaps it required the metal container to be resealed, while other solutions were sometimes big and bulky, or untested and may not be reliable in the worst-case scenarios.

The risk with these solutions is the reliability of the seal. Ensuring that the container has no openings is also critical. This would allow electromagnetic radiation to penetrate to the interior of the cage or container. After much research that yielded no comparable solution and the successful prototyping of this gasket design, I found this to be the right opportunity to describe how this gasket is made and installed.

The Solution

The solution is a very effective metallic gasket, using sheet metal and tinned copper mesh tape. The gasket can be made with readily available materials and tools, and it requires only modest mechanical skills. The gasket makes nearly any metallic military surplus ammunition can into a very effective faraday cage and container.

The cost of materials for each gasket is in the range of $8 to $15 dollars, depending on the size of the gasket and the desired “belt-n-suspenders” to enhance the effectiveness of the gasket and container.

My Objective

In the most recent design challenge, I sought a solution that was reliable, convenient, and would help to organize the storage of sensitive electronic equipment. Most people are unlikely to build or can afford a faraday room or closet to protect electronic equipment. Furthermore, I don’t have the space to accommodate several galvanized garbage cans or 55-gallon metal drums in our garage or basement. A solution that provides protection from radio frequency or electromagnetic interference while providing convenient access and meeting the waterproof and airtight requirements was the optimal and desired solution.

Organizing these solutions to make each interoperable would also be valuable. Finally, convincing our family members of the value of such a solution is another challenge. Any solution has to be something that the whole family will value. More importantly, it must be something where they won’t be intimidated to use the solution in an emergency or in everyday use.

The Beginning- The Ammunition Can

As a starting point, there are a variety of ammunition cans for consideration, including the big 120mm mortar cans. These mortar cans are 32” by 12” by 5½”. The 40mm can is 17½” by 10” by 6”. An 11” by 5½” by 7” option is the 50mm can. In my opinion, the best can is the 20mm variety; it’s not too big, not too small, and won’t be too heavy to move. But all of these ammo cans will accommodate a variety of sensitive electronics of all sizes and shapes.

The 20mm M548 ammo can is a personal favorite and has inside dimensions and usable space that measures 17 1/4″ by 14 1/16″ by 7 3/8″. Outside dimensions, with the lid attached, measure 18 5/8″ by 14 7/16″ by 8 3/8″. These 20mm ammo cans will easily accommodate a laptop and tablet with power cables, or an inverter up to 2,500 watts, or a small 20 to 40 amp solar charger and controller. It also provides a way to build a battery bank to run equipment like HF or VHR/UHF radios, on an inverter.

Directions For Building Ammo Can Gaskets

The following instructions and pictures describe how to make almost any ammo can resistant to the effects of Radio Frequency (RF) or EMP (Electromagnetic Pulse) interference, including the likely effects from a geomagnetic solar storm. The solution retains the well-known water resistant and airtight effectiveness of these ammo cans. These cans may be easily opened and closed without compromising the shielding effectiveness of the gasket.

To make these gaskets you will need the following materials, tools, and hardware:

1. A sheet of 18 to 24 gauge metal

Galvanized sheet metal will work, but you may also use standard hot rolled unfinished sheet metal. If you want to splurge, you could use copper metal sheets that will be more expensive, but you’ll have the “Cadillac of gaskets”. Don’t use aluminum or stainless steel sheets for reasons that will be more obvious in the construction of the gasket. The size of the sheet metal needed will depend on the size of gasket you are making. So I suggest that you start by purchasing a 12” by 24” sheet, which are readily available at big box hardware stores. This size will make two or three gaskets, including at least one for the big 20mm cans or the 120mm mortar cans. Cost: $4 to $12 per sheet.

2. 3M Scotch 24 Copper Mesh Electrical Shielding Tape that’s rated from 32 to 220 Degree F.

The tinned copper tape mesh roll is 15′ long by 1″ wide. This product may be hard to locate but is generally found on eBay for $12 to $25 per roll. Other online retailers also carry the product. The product is a very thin, flexible tape made of tinned copper mesh. The construction of the tape makes it easy to solder the product to a properly prepared metal surface. In the early prototypes of the gasket, I was unsuccessful in using flat tinned copper braid. This product is generally too thick and makes it difficult to seal the lid to the can. In future prototypes, I may try to split this braid and use only a single layer in lieu of the mesh tape. Cost: $12 to $20 per roll which is usually enough to complete two or three gaskets.

3. Straight Cut Sheet Metal and Aviation Snips.

Cost: $5 to 16. However, you can find these at garage and estate sales, or you might borrow a pair of snips from a friend. You might also ask a local heating and ventilation contractor to cut a piece of sheet metal to size for this project.

4. Lead/Tin Solder, Rosin-based

I prefer to avoid the acid core solder that will corrode metal if not thoroughly cleaned. However, some would suggest a good acid based flux and 50/50 solder using a high wattage iron works the best. I’ve also had good experience with thin 60/40 solder with rosin paste flux. However, don’t use a torch of any kind. It will degrade the galvanize and will never allow the solder to flow properly. Also from one bad experience, I can tell you it will burn up the mesh shielding tape. Cost: $3 to $5 for flux and solder.

5. Soldering Gun or Pencil

You will need at least 100-watt soldering iron, and it is better to have more heat than less if your sheet metal is of a thicker gauge. Cost: $25 to $55, depending on the wattage and features. However, again you might find a friend with an iron and build some gaskets together to avoid this expense.

6. Phillips Head Sheet Metal Screws

It is preferable to use steel screws in size #6 x ¼” or #8 x ¼” that are self-tapping. These can be found online or at the local hardware store. Alternatively, a #8 or #6 Philips head counter sunk screw with a finishing washer will make a nice enhancement (see picture). Important assembly step: the screws can’t be longer than 3/8” and the preferable length is ¼”. It may be hard to find these steel screws, but keep at it. These lengths are the only size that will work to properly secure the gasket. You will also need a power drill and a 3/32” steel drill bit for the pilot hole to start the screws. Cost: $1 to $3, depending on the source and use of finish washers.

7. Sand Paper or coarse Steel Wool

The sand paper or wool is to remove any paint where you will need “bare metal-to-metal” contact. A dremel tool is a handy way to remove paint in small areas and will have many other uses around the workshop. Cost: Minimal (for sand paper or steel wool). A starter Dremel Tool kit can be found for less than $25 or borrowed from a neighbor or friend.

8. M548 20mm Ammo Can

This can must be in good condition with no penetrating dents or any bent or dented edges that would prevent a good contact and seal with the rubber gasket on the lid. Finally, it must have good seams that are not rusted or split or badly corroded. For this project and the several ammo cans that have been enhanced with the shielding gasket, these cans are painted with flat paint, using different colors (black, brown, and green) to distinguish what’s in the various ammo cans. (I have more on this later.) Cost: $5 to $45 per can, depending on the size of the can, condition, and cost of shipping. I am able to consistently find these 20mm cans at gun shows or military surplus stores for $35 dollars. They are usually in very good condition.

SurvivalBlog Writing Contest

This has been part one of a four part entry for Round 71 of the SurvivalBlog non-fiction writing contest. The nearly $11,000 worth of prizes for this round include:

First Prize:

1. A $3000 gift certificate towards a Sol-Ark Solar Generator from Veteran owned Portable Solar LLC. The only EMP Hardened Solar Generator System available to the public.
2. A Gunsite Academy Three Day Course Certificate. This can be used for any one, two, or three day course (a $1,195 value),
3. A course certificate from onPoint Tactical for the prize winner’s choice of three-day civilian courses, excluding those restricted for military or government teams. Three day onPoint courses normally cost $795,
4. DRD Tactical is providing a 5.56 NATO QD Billet upper. These have hammer forged, chrome-lined barrels and a hard case, to go with your own AR lower. It will allow any standard AR-type rifle to have a quick change barrel. This can be assembled in less than one minute without the use of any tools. It also provides a compact carry capability in a hard case or in 3-day pack (an $1,100 value),
5. An infrared sensor/imaging camouflage shelter from Snakebite Tactical in Eureka, Montana (A $350+ value),
6. Two cases of Mountain House freeze-dried assorted entrees in #10 cans, courtesy of Ready Made Resources (a $350 value),
7. A $250 gift certificate good for any product from Sunflower Ammo,
8. Two cases of Meals, Ready to Eat (MREs), courtesy of CampingSurvival.com (a $180 value).

Second Prize:

1. A Model 175 Series Solar Generator provided by Quantum Harvest LLC (a $439 value),
2. A Glock form factor SIRT laser training pistol and a SIRT AR-15/M4 Laser Training Bolt, courtesy of Next Level Training, which have a combined retail value of $589,
3. A gift certificate for any two or three-day class from Max Velocity Tactical (a $600 value),
4. A transferable certificate for a two-day Ultimate Bug Out Course from Florida Firearms Training (a $400 value),
5. A Trekker IV™ Four-Person Emergency Kit from Emergency Essentials (a $250 value),
6. A $200 gift certificate good towards any books published by PrepperPress.com,
7. A pre-selected assortment of military surplus gear from CJL Enterprize (a $300 value),
8. RepackBox is providing a $300 gift certificate to their site, and
9. American Gunsmithing Institute (AGI) is providing a $300 certificate good towards any of their DVD training courses.

Third Prize:

1. A Royal Berkey water filter, courtesy of Directive 21 (a $275 value),
2. A custom made Sage Grouse model utility/field knife from custom knife-maker Jon Kelly Designs, of Eureka, Montana,
3. A large handmade clothes drying rack, a washboard, and a Homesteading for Beginners DVD, all courtesy of The Homestead Store, with a combined value of $206,
4. Expanded sets of both washable feminine pads and liners, donated by Naturally Cozy (a $185 retail value),
5. Two Super Survival Pack seed collections, a $150 value, courtesy of Seed for Security, LLC,
6. Mayflower Trading is donating a $200 gift certificate for homesteading appliances,
7. Montie Gear is donating a Y-Shot Slingshot and a $125 Montie gear Gift certificate.,
8. Two 1,000-foot spools of full mil-spec U.S.-made 750 paracord (in-stock colors only) from www.TOUGHGRID.com (a $240 value), and

Round 71 ends on July 31st, so get busy writing and e-mail us your entry. Remember that there is a 1,500-word minimum, and that articles on practical “how to” skills for survival have an advantage in the judging.