You own a rugged military surplus ammo can, but its standard latch offers zero real security against prying hands. Whether you are storing emergency cash, sensitive documents, or small valuables, learning how to lock an ammo box properly turns this durable container into a portable safe.
This guide details two proven methods to secure your gear without ruining the waterproof seal. You will learn a zero-tool technique using the existing lug and a permanent drilled option for maximum protection.
Secure Your Can Using the Non-Invasive Lug Method
This technique utilizes the built-in locking lug to trap a padlock shackle. It requires no drilling and leaves the original factory seal completely intact. This is the ideal choice for renters or anyone needing a reversible solution.
Lift the Locking Lug Upward
Close the lid firmly until you hear it click into place. Locate the small metal tab known as the locking lug near the hinge on the lid. Instead of pushing it down over the front latch, lift the lug upward until it snaps over the top rim of the can body.
This action creates a narrow gap between the lifted lug and the metal rim. The lug now forms a natural loop that acts as a shackle hole. Your goal is to position a lock here so it physically blocks the lid from lifting off the body.
Insert a Long-Neck Padlock
You must use a long-neck padlock with an extended shackle to fit through the gap created by the lifted lug. Standard short-shackle locks will not fit or provide enough clearance to be effective.
Slide the shackle through the opening between the lug and the rim, then snap it shut. Once locked, the shackle prevents the lid from rising even if someone forces the lug back down. The lock becomes a structural barrier that stops unauthorized access.
Pro Tip: Master Lock long-neck models like the #175 or #3 fit perfectly in most 30 and 50-caliber cans due to their specific shackle width and length.
Avoid These Common Mistakes
Using the wrong hardware or technique can render your security efforts useless. Avoid these specific errors to ensure your container remains secure.
- Using a short-shackle lock: The shackle will not reach through the gap, allowing the lid to lift easily.
- Leaving the lug in the down position: Without lifting the lug, there is no space for the lock to trap the lid.
- Failing to close the lid fully: A loose seal defeats the purpose of a weatherproof container and makes prying easier.
Install a Permanent Lock Plate via Drilling
Installing a lock plate converts your ammo can into a true portable safe with a built-in locking point. This permanent method takes about ten minutes and costs less than ten dollars but delivers a professional appearance.
Gather Required Tools and Parts
You need specific items to complete this conversion successfully. Ensure you have everything ready before starting the drilling process.
- Standard metal ammo can (30cal or 50cal)
- Lock plate conversion kit with bits and washers
- Power drill and file or deburring tool
- Locking pliers and thin flathead screwdriver
- Stick-style Loctite thread locker
- Recommended padlock like the Pack Lock Pro 9A
These kits are widely available online and often include the necessary pilot and stepper drill bits for a complete installation.
Drill the Pilot Hole First
Choose a spot on the lid near the edge opposite the hinge for easy access. Use the pilot drill bit from your kit to create a small starter hole that guides the larger bit and prevents slipping.
Switch to the stepper drill bit to cut a clean, tapered hole in the thin metal. Apply steady pressure and let the bit work until it notches through the metal. You will feel a slight drop when the hole is complete, and minor metal blowout is normal.
Smooth and Clean the Edges
Use a file to remove sharp burrs from the inside edges of your new hole. Rough edges can damage the rubber washer, wear down your padlock shackle over time, or prevent the lock plate from seating flush.
Deburring ensures a tight and clean fit for your hardware. This step protects your investment and maintains the structural integrity of the installation point.
Apply Thread Locker to the Nut
Take the locking nut from your kit and apply a small amount of stick-style Loctite to its threads. This adhesive prevents vibration from loosening the assembly over years of use.
Avoid liquid thread locker as it can drip and contaminate the interior of your can. Stick Loctite provides a mess-free application that is just as effective for securing the nut.
Assemble the Lock Plate Components
Stack the components in the correct order to ensure a proper seal and strong connection. The rubber washer must go against the lid to seal out water and dust.
- Place the rubber washer against the lid surface.
- Add the metal washer to reinforce the connection.
- Position the lock plate with the eyelet facing outward.
- Thread the locking nut with Loctite onto the assembly.
Insert the entire assembly through the hole from the top side of the lid. Use locking pliers to tighten the nut securely without over-tightening and damaging the components.
Align the Eyelet Horizontally
Orient the lock plate so the eyelet runs east to west in a horizontal position. Do not install it north to south in a vertical orientation.
A horizontal alignment allows the padlock shackle to move freely when you open and close it. If installed vertically, the shackle may bind or get stuck, making it difficult to remove even when unlocked. Use a thin flathead screwdriver through the eyelet to hold and rotate the plate while tightening.
Attach the Padlock Securely
Slide the shackle of your padlock through the installed eyelet once the plate is secure. Some kits include a secondary washer to cap the shackle and prevent shimming attempts.
To open the container, simply unlock the padlock, remove the shackle and any retaining washer, then lift the lid. The result is a sleek and integrated lock point that looks like it came from the factory.
Compare Both Locking Methods for Your Needs
Choosing the right method depends on your priorities regarding speed, reversibility, aesthetics, and long-term security requirements.
Hardware Compatibility Differences
| Feature | Non-Invasive Method | Drilled Method |
|---|---|---|
| Best Lock Type | Long-neck padlock | Compact pick-resistant lock |
| Lock Removal | Easy with no tools | Easy but plate stays installed |
| Upgrade Path | Limited to padlock only | Can bolt can to floor or wall |
The Pack Lock Pro 9A is recommended for drilled setups because it is small and fits snugly in tight eyelets. For non-invasive use, a long-shackle padlock is non-negotiable since short ones will not work.
Cost and Time Comparison
| Factor | Non-Invasive | Drilled |
|---|---|---|
| Tools Needed | None | Drill, file, pliers |
| Setup Time | 10 to 15 seconds | Less than 10 minutes |
| Cost | One-time padlock purchase | Approximately $6 per kit |
| Reusability | Unlimited with no damage | Permanent with hole remaining |
If you already own a long-neck padlock, the non-invasive method costs nothing extra. The drilled option pays for itself in durability if you are securing multiple cans permanently.
Seal and Structural Integrity
The non-invasive method preserves the 100% waterproof and dust-proof seal since nothing punctures the body. The drilled method maintains the seal if the rubber washer is properly compressed and the hole is clean.
Neither method compromises the fire resistance or overall strength of the steel body. The gasket on the lid still seals the rim effectively in both scenarios when installed correctly.
Security Level Assessment
The non-invasive approach offers good deterrence for casual access prevention. The drilled method provides better resistance to prying and forced entry attempts.
For high-value storage or vehicle use, the drilled method allows you to bolt the can down. This turns the container into a fixed safe that is much harder to steal entirely.
Choose the Right Method for Your Needs
Your specific use case should dictate which locking method you choose for your ammo box. Consider your tools, timeline, and long-term goals.
Use Non-Invasive If
- You are renting or borrowing the can temporarily.
- You need a quick lock without any commitment.
- You want to preserve resale or collectible value.
- You lack tools or DIY confidence for drilling.
This method is perfect for preppers and campers needing fast access with zero modification to the container.
Choose Drilled Conversion If
- You want a clean and permanent locking solution.
- The can will be stored in a vehicle or fixed location.
- You plan to bolt the can to a surface for theft prevention.
- You value a professional and integrated appearance.
It is ideal for storing firearms separately from ammo, emergency cash, or sensitive documents that need higher security.
Maintain Your Locked Ammo Box
Even the best lock requires care to last through years of use. Regular maintenance ensures your security setup remains reliable.
Padlock Maintenance Tips
- Lubricate the keyway annually with graphite spray instead of oil.
- Wipe down the shackle to prevent rust in humid climates.
- Store the lock unlocked when not in use to reduce spring tension.
Inspect the Seal Regularly
Check the rubber gasket every six months for cracks or compression loss. Clean it with mild soap and water while avoiding harsh chemicals that degrade rubber. Re-seat the lid occasionally to maintain seal integrity.
For Drilled Cans Check the Plate
Tighten the nut if the plate feels loose after years of vibration. Ensure the Loctite bond has not degraded and reapply if needed. Confirm the eyelet still moves freely with the padlock inserted.
Frequently Asked Questions About Locking Ammo Boxes
Can I lock an ammo box without drilling holes?
Yes, you can lift the existing locking lug upward and insert a long-neck padlock through the gap. This method secures the lid without damaging the can or compromising its waterproof seal.
What type of padlock fits the non-invasive lug method?
You need a long-neck padlock with an extended shackle, such as the Master Lock #175 or #3. Standard short-shackle locks will not fit through the gap created by the lifted lug.
Does drilling a hole ruin the waterproof seal of the can?
No, if you use a conversion kit with a rubber washer and tighten it correctly. The rubber washer seals the drilled hole while the main lid gasket keeps the rim sealed.
How much does a lock plate conversion kit cost?
A single conversion kit typically costs around $6, while a four-pack with drill bits costs approximately $15. This is a low-cost way to create a permanent locking point.
Which method is better for securing a can in a vehicle?
The drilled conversion method is better because it allows you to bolt the can directly to the vehicle floor. This prevents thieves from simply stealing the entire container.
Key Takeaways for How to Lock an Ammo Box
Securing your ammo box is simple when you choose the right technique for your situation. The non-invasive lug method offers instant security with zero tools, while the drilled lock plate provides a permanent and professional solution.
Both methods transform a standard metal can into a secure storage unit for your valuables. Select the approach that matches your needs, gather your hardware, and lock your gear with confidence today.
