Corrosive Ammunition: Rust Inducing Nightmare or Cheap Plinking Fun?

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Whenever the term ‘corrosive ammo’ gets tossed around new shooters, most of them recoil like a vampire exposed to sunlight. They think that shooting corrosive ammunition is akin to dumping highly concentrated sulfuric acid down the bores of their handguns or rifles.

This couldn’t be further from the truth.

Although using corrosive ammo will corrode and pit the internals and barrel of your firearm, you can comfortably shoot corrosive surplus ammunition so long as you follow the proper cleaning procedures that we will outline in this article.

I hope you bought a can opener for that spam can of military surplus ammo because we are going to pull the trigger on some corrosive ammo and learn what it is, what it isn’t, and how to ensure your firearm is clean and protected from corrosive ammunition.

What is Corrosive Ammo?

Corrosive ammo is a bit of a misnomer as the ammo itself is not corrosive, however, the primers in this ammo contain a priming compound that utilizes corrosive salts. Once fired, these corrosive salts will be deposited in the barrel, gas system, bolt, and chamber of your firearm and begin to corrode unless properly and quickly removed.

How can you tell if ammo is corrosive?

Unless stated on the ammo container, all military surplus ammo that is Berdan primed should be assumed to be corrosive, while Boxer primed ammo will be non-corrosive.

To understand how corrosive primers came about, it’s a good idea to take a quick look at how centerfire cartridges, primers, and primer chemistry evolved over the years.

Evolution of Corrosive Primers

Between 1808 and 1812, the Swiss gunsmith Jean Samuel Pauley created the first centerfire cartridge which utilized a percussion cap as the primer. A percussion cap utilizes mercury fulminate as the priming compound as it is very effective at igniting black powder.

Although mercury fulminate excels at igniting black powder, smokeless powder exposed the shortcomings of the percussion cap.

Mercury fulminate will slowly decompose over time, meaning that eventually, the percussion cap will lack the energy required to ignite the smokeless powder. This was never realized as an issue with black powder, as black powder is so combustible that even static electricity can ignite it.

The next evolution of priming compound was adding potassium chlorate to the mercury fulminate to stabilize the mixture. However, this evolution presented new problems.

Higher pressure smokeless powder rounds would leave mercury deposits inside the barrel and the brass cartridge case. The mercury coating would embed itself into the brass, therefore weakening it and making reloading impossible.

The US Military decided to stop the use of mercury-based primers in 1898 and began working on a new primer system. Frankford Arsenal proposed the FA-70 primer that utilized potassium chlorate as an oxidizer for lead thiocyanate.

The FA-70 Primer is corrosive and here’s why:

Once fired, potassium chlorate or sodium perchlorate primers will deposit corrosive salts into the barrel and internals of the firearm. These corrosive salts are potassium chloride and sodium chloride.

For all my chemistry savvy readers, you’ll note that sodium chloride is table salt.

Now, neither of these salts are corrosive on their own…I mean you wouldn’t think that you’re adding corrosive material to your favorite cut of meat at the dinner table!

However, potassium chloride and sodium chloride are hygroscopic. That’s a fancy chemistry word that means they will attract water from humidity in the atmosphere. Once combined with water, the corrosive salts will begin to corrode anything with which it comes into contact (think of how saltwater quickly rusts exposed metals).

For US Military surplus ammo, most of what is available will be non-corrosive. However, there are some lots that you might find in the wild that are older and have corrosive primers.

Any military surplus ammo bearing these headstamps (located around the primer pocket) or earlier will be corrosive:

• .45 ACP: FA 54, FCC 53, RA 52, TW 53, WCC 52, WRA 54
• .30-06 Springfield: FA 56, LC 52, RA 51, SL 52, TW 52, WCC 51, WRA 54, FN 57

Any surplus you find with those headstamps that has a higher date will be boxer primed and non-corrosive.

However, Russian and Yugo military surplus ammo is the most common corrosive ammo on the market. So how do you tell if this Comm Bloc ammo is corrosive or not?

A good rule of thumb is that if it comes in a spam can, it’s corrosive – for example, Yugo M67 ball, which some shooters describe as “mildly corrosive.”

Gone unchecked and uncleaned, corrosion will set in and invite a host of additional firearm problems regardless of how “mildly corrosive” an ammo lot is.

All modern Russian produced ammo (e.g. 7.62x39mm, 5.45x39mm, 7.62x54R) will be Berdan primed but will be non-corrosive. It should say so on the box.

What happens if you do shoot corrosive ammo in your firearm? Is your prized rifle or handgun doomed to a life in the rust bucket?

Not at all! There’s a cleaning procedure that, if you follow, will remove the corrosive salts from your firearm.

Cleaning Corrosive Ammo

The key to safely shooting corrosive ammo is getting all those corrosive salts out of your barrel and internals of your firearm using the most powerful solvent known to man.

Now I’m guessing you’re racking your brain right now trying to figure out what it is! And it’s NOT Break-Free CLP, Ballistol, or even the venerable Hoppes #9. It is none other than surfactant-infused dihydrogen oxide.

Also known as: Soapy Water

I know that this isn’t glamorous, but boiling water with soap is the best thing you can use to remove corrosive salts – and if you think about it, it makes perfect sense.

If you wanted to dissolve salt in the kitchen, would you use vegetable oil or water? Obviously, water is the superior choice, it’s just not something that we think of when we’re cleaning our firearms.

Here’s the procedure for cleaning your handguns or rifles after shooting corrosive ammo:

Step 1: Remove all copper and carbon fouling from the barrel.

Corrosive salts can become trapped beneath coper fouling and/or carbon fouling that ends up in your barrel from the firing procedure. Therefore, we need to get that out first.

Use your favorite gun cleaning solvent like Hoppes, Ballistol, or Break-Free CLP to thoroughly clean your barrel. A foaming bore cleaner is also acceptable.

Push a dry patch through with a jag when your barrel is sufficiently clean (always push patches and brushes from the chamber to the end of the barrel).

Step 2: Wash out the corrosive salts with soapy water.

The next step is to wash out the corrosive salts left by the corrosive primers. This is done simply by soaking your firearms parts in hot water or by pouring boiling water down the bore of your rifle (if submersion is not ideal). Boiling water is ideal as it evaporates quicker.

This step can be particularly tricky for semi-auto rifles because you need to thoroughly clean the gas system as this is where most of the corrosive salts will reside. My recommendation is to not shoot corrosive ammo in Direct Gas Impingement (DGI) rifles like the AR-15, as disassembling the gas system is a massive pain.

However, for short stroke gas piston rifles like the SKS and the AK-47, this is not too difficult to accomplish as these gas systems were designed to field strip easier.

Make sure to pay special attention to the bolt face and bolt carrier group as there are lots of little nooks and crannies that corrosive salts can sneak into.

There are some gunsmiths who recommend soaking in water combined with CLP or Ballistol. These oils will both clean and lubricate your firearm parts after you remove them from the water, eliminating the need to dry your parts off.

I cannot attest to the effectiveness of these methods as I’ve not tired them. Every time I fired corrosive ammo in my Mosin Nagant, I simply used hot water or Windex to clean off my rifle parts.

Speaking of Windex, let’s discuss that for a moment.

There are some folks on the Internet that suggest the ammonia in Windex will “neutralize” the corrosive salts in surplus ammo. To put it bluntly, this is just silly.

The ammonia in Windex does nothing to remove corrosive salts, it’s there to make the water in the Windex evaporate quicker. You can use Windex to clean your firearm parts and bore, but make certain it is the unscented, original Windex with actual ammonia in it (some new versions use an analog).

Step 3: Lubricate your firearm.

Water can corrode your firearm just as fast as corrosive salts can, therefore the next step is to displace all of that water we just introduced into our gun.

If you used the water-Ballistol or water-CLP mixture in the previous step then you should be good to go.

However, if you used my method, then you’ll need to thoroughly lube anything that came in contact with water in the previous step.

Whichever lube you use is completely up to you. My two favorites are Weapon Shield and Break-Free CLP.

Regardless of which you pick, liberally lube your gun parts to ensure that all of the water is displaced by gun oil. I’d also recommend running a patch soaked with oil down the bore of your firearm to ensure that all water has been removed from the barrel.

Step 4: Put yout firearm in the safe and crack a tasty beverage

You’re done! That’s all there is to it!

Corrosive vs. Non-Corrosive Ammo

Now if you thought that the cleaning procedure outlined in the previous section sounds like a bit of a pain, well you’re right…it is!

There are definitely pros and cons of when you shoot corrosive ammo, so let’s consider them before we pull the trigger on that Russian spam can of 7.62x54R for your Mosin Nagant.

Pros of Corrosive Ammo

As mentioned earlier, corrosive ammo is typically military surplus. This means it’s cheap and you can buy it in bulk. Reducing the cost of shooting for an added step in cleaning is worth it for many shooters.

Furthermore, it has sufficient accuracy at this price point. You aren’t going to get match-grade ammo when you buy surplus but it will do the job.

Surplus ammo is also very shelf stable and is typically packed for long term storage in spam cans or battle packs. These surplus ammo options are hermetically sealed and this makes it ideal for stocking up for a “rainy, tyrannical day.”

Lastly, the primers are extremely reliable. The US Military issued corrosive ammo throughout WWI, WWII, and Korea – yes, my grandpa was carrying corrosive ammo for his M1 Garand in Guam during WWII. These primers have been proven to be incredibly stable and reliable under demanding battlefield conditions as well as remaining effective during long term storage.

Cons of Corrosive Ammo

The biggest negative aspect of corrosive ammo is the added cleaning steps. If your firearm is not cleaned properly after firing, then it will look like the bad end of a sewer pipe in no time. It’s recommended that you clean your firearms immediately after returning home from a range trip using corrosive ammo.

Another downside of corrosive ammo is that it is not suitable for reloading. As most military surplus ammo is Berdan primed, this makes it extremely difficult to reload. Furthermore, most all Russian ammo is steel cased which cannot be reloaded either.

Lastly, corrosive ammo, and specifically military surplus ammo can become the victim of regulations on import-export laws. Like we’ve seen recently with the ban on the importing of Russian ammo or the banning of 7N6 surplus ammo in times past, the government can create massive supply/demand issues when it comes to the importation of cheap, military surplus ammo.

Pros of Non-Corrosive Ammo

Since the 1920s, commercial ammo manufacturers began selling their ammunition with non-corrosive primers to avoid all of the downsides of corrosive ammo. Here are some of the major benefits of using non-corrosive ammo in your firearms.

Non-corrosive ammo is very popular because it doesn’t corrode your firearm…imagine that! This means you do not need to go through a laborious cleaning procedure when it’s time to do your post-shooting maintenance routine. However, if you do not have time to clean your guns immediately after going to the range, it’s not a big deal and you will not be greeted by corrosion when you get to cleaning your guns.

Non-corrosive ammo is typically Boxer primed, this means that reloading is a breeze. If you like to reload your ammo like me, then this is critically important when purchasing new ammo because you want to reuse the brass casings.

Another benefit of non-corrosive ammo is that there are tons of different manufacturers to choose from. Winchester, Hornady, PMC, Federal, Remington, Speer, and American Eagle are just a few of the companies that produce non-corrosive ammo and each of them have their own unique offerings to cater to your shooting needs.

Lastly, there is ample supply of non-corrosive ammo available across North America. Military surplus ammo is typically tied to import laws and restrictions, meaning government interference can cause supply and demand issues for military surplus ammo. This is not the case for domestically produced non-corrosive ammo.

Cons of Non-Corrosive Ammo

Although there are ample reasons to purchase non-corrosive ammo, there are some negatives that we need to address as well.

The first being cost – non-corrosive ammo is always going to be more expensive than corrosive ammo. Although many shooters do not mind the added cost, some sportsmen are on a limited budget, and this is something to take into consideration.

Another negative of non-corrosive ammo is the potential for corrosion of the cartridge case itself. Brass is corrosion-resistant, but that doesn’t mean that it’s corrosion proof! As most non-corrosive ammo is typically not hermetically sealed in spam cans or battle packs, the brass casings will be more prone to corrosion over time when compared to sealed military surplus ammo.

Conclusion: Corrosive Ammo

No matter what type of shooting you enjoy, whether it be plinking around with your semi-auto rimfire rifle, pulling out dad’s old Winchester Model 101 over/under 12-gauge to shoot some skeet, or sighting in that milsurp Mauser or British Enfield you just picked up at the gun show, there’s no reason to shy away from using corrosive ammo.

The reduced cost and long shelf life of corrosive surplus ammo makes it ideal for stocking up, and you can rest assured that it will fire when the time comes for you to use it.

Although it is not recommended to use corrosive ammo in your AR-15 due to the difficulty of cleaning the DGI gas system, you should not shy away from using it in your SKS or AK-pattern rifles as the short stroke gas piston is easy enough to disassemble and clean.

Understanding what corrosive ammo is and how to clean your firearm after shooting it is the key to preventing corrosion on your firearm.

In conclusion, there’s no reason to fear corrosive ammo as it offers you more trigger time on your firearms at a reduced cost. The only thing you need to do is clean your firearms immediately when you get home, following the procedure outlined in this article, and there should be no reason you ever see rust on your firearms after shooting corrosive ammo.

Corrosive Ammo: Rust Inducing Nightmare or Cheap Plinking Fun? originally appeared in The Resistance Library at Ammo.com.