Ammunition Oil Guide for Steel, Aluminum & Polymer Mags

If you spend much time around serious shooters, you hear a lot of talk about optics, barrels, and trigger jobs. You do not hear enough about magazines and the oil that ends up on them and on the ammo they feed. That is a mistake. Your magazines are consumable parts, but they are also the single most common failure point in a rifle or pistol. How you use and store oil on them, and what those mags are made of, dictates how long they keep working.

This is a practical, no-fluff breakdown of how ammunition oil and gun lubricants interact with steel, aluminum, and polymer magazines, based on corrosion science and what working shooters and armorers actually do in the field. The goal is simple: protect your gear, avoid self‑inflicted malfunctions, and spend your money on ammo and training instead of preventable replacements.

Why Magazine Material Matters More Than Brand Names

Before we talk oil, you need to understand what you are actually putting that oil on. Primary Arms’ magazine maintenance guide makes a point that most shooters gloss over: magazine bodies and springs are not all the same, and the material choice drives how you should protect them.

Polymer magazines are the most common today. They are light, tough, and shrug off a lot of environmental abuse. Modern, quality designs hold their feed lips well even when stored loaded for long periods, and the usual worry about long‑term deformation is largely a legacy issue. The downside is that once a polymer body cracks or splits, you are done. There is really no structural repair, so you treat them as disposable when they fail.

Aluminum magazines sit in the middle. They are light and reasonably corrosion‑resistant, but more prone to bent feed lips and dents from hard drops. You can often coax them back into shape, but repeated impacts and metal fatigue eventually cause feeding issues. They are forgiving, but not magic.

Steel magazines are the tanks. They are generally the toughest and often repairable, which is why they are so common on AK‑pattern rifles and older service guns. The price you pay is weight and rust risk. Primary Arms notes that steel is best suited to dry climates and becomes more of a liability in wet environments.

Across all these materials, the springs are almost always steel. Primary Arms is blunt about the main long‑term threat to stored magazines: rust, including corrosion of stainless springs buried inside polymer and aluminum bodies. That is the anchor point for everything else in this article. Oil exists in this context to manage corrosion and friction. Get that wrong, and your magazine material choice cannot save you.

What Ammunition Oil Actually Does

When most people say “ammunition oil” they mean the same light gun oils, CLPs, or corrosion inhibitors they use on firearms. Those products do a few critical things to metal surfaces.

First, they change how the surface interacts with water. In corrosion research on pipelines and crude oil systems, engineers talk about whether a steel surface is “water‑wet” or “oil‑wet.” When bare steel stays covered in water, corrosion accelerates. When surface‑active organic compounds from oil coat the metal and make it more oil‑wet, that water contact is interrupted and corrosion slows. Studies of CO₂ pipeline and crude‑oil corrosion show that a thin, continuous organic film can cut corrosion rates dramatically by limiting water access, but once that film is compromised and water droplets intermittently hit bare spots, localized attack ramps back up.

Your gun oil is doing the same basic job. A light oil film on a steel magazine body or spring acts as a barrier between the metal and moisture. It shifts the surface toward “oil‑wet” instead of “water‑wet.” That is corrosion inhibition in plain English.

At the same time, oil is a magnet for everything else in your environment. Sarco Inc’s rifle magazine maintenance guide warns that after cleaning a steel AR‑15 mag you should apply only a very thin coat of protectant inside and outside, because excess oil attracts dust, sand, and other particulate. Primary Arms makes a similar point at the storage level: for very long‑term storage of steel magazines they prefer a grease coating on springs and exteriors, but they insist that grease be removed before the magazine goes into service because it will hold dirt and fouling.

So the real job of ammunition oil in and around your magazines is to walk a narrow line. It should:

Keep bare steel surfaces oil‑wet enough that moisture cannot sit on them for long.

Avoid building up thick, sticky layers that trap grit and slow down the follower.

Protect the spring and any exposed carbon steel while letting the magazine run fast and reliably.

How that balance looks depends heavily on the magazine material.

Steel Magazines: Oil, Rust, And Realistic Service Life

Steel magazines live or die by how you handle oil and moisture. They are mechanically robust, but the same traits that make steel strong also make it the most vulnerable to rust if you get lazy.

On the prevention side, pistol and rifle shooters on forums like Primary & Secondary and SIG Talk keep the guidance simple: keep metal magazines lightly oiled. Light is the operative word. A thin film on the exterior and interior steel surfaces blocks moisture, but does not leave puddles. SIG Talk users add a wrinkle that fits real carry habits: wiping down a mag with a silicone‑impregnated rag after handling adds a supple film that fights corrosion without leaving visible wetness, which is especially useful when magazines ride against sweat and clothing.

Sarco’s step‑by‑step cleaning process for a steel AR‑15 box magazine fills in the mechanical details. After clearing the weapon and unloading the mag, they strip the floorplate, follower, and spring. They scrub the steel body with a fouling solvent, wipe down the interior and exterior, and then apply a very thin coat of protectant such as Rem Oil. They emphasize that you should clean the follower and spring thoroughly, but that the spring itself should be reinstalled completely dry. The body gets a film; the spring is kept clean and oil‑free to discourage dirt buildup.

For long‑term storage, Primary Arms and an AK‑focused storage thread both tighten the screws on corrosion prevention. Primary Arms recommends sealing stored magazines in containers such as MIL‑SPEC ammo cans with desiccant packs to keep humidity low. For very long storage, they suggest a light coating of grease on magazine springs and the entire exterior of steel bodies. Grease stays put better than oil and offers stronger rust protection in a stable storage environment, but absolutely must be removed before use because it attracts dirt, sand, and fouling.

The AK forum thread adds a critical caution that too many people ignore: do not store bare steel magazines in direct contact with plastic. When you put oiled or bare steel directly into plastic bags or bins, you can trap residual moisture and any off‑gassing from the plastic against the metal. Over time this encourages corrosion instead of preventing it. Their solution is straightforward. Clean each magazine and apply a light coat of your preferred gun oil. Wrap each in acid‑free paper, tape it shut, label it with the mag’s identity and the date, and only then put it into a heavy‑mil zip bag with desiccant. The paper is a neutral barrier that separates steel from plastic while still allowing micro‑venting and moisture buffering.

In practice that means this: steel magazines that stay in rotation for classes or duty get minimal oil and regular cleaning. Steel magazines that are essentially stored as long‑term assets get a more aggressive rust‑proofing treatment plus a controlled environment. In both cases, the material’s weakness is rust, and oil is your main tool to control it without damaging function.

Aluminum Magazines: Light, Corrosion‑Resistant, But Not Immortal

Aluminum magazines behave differently. They do not “rust” in the red‑flake sense like steel, but they can corrode and their finishes can degrade, especially around scratches, dents, and seams where moisture sits. Primary Arms points out that aluminum mags are light and fairly corrosion‑resistant, but take a beating at the feed lips and body from drops and impacts, which can cause reliability problems long before you see obvious corrosion.

From a lubrication standpoint, aluminum magazine bodies do not need the same level of heavy rust‑proofing as bare steel, but their internal springs and any steel inserts still do. Primary Arms explicitly notes that rust on magazine springs is a primary long‑term failure mode, even inside aluminum or polymer bodies.

That leads to a hybrid approach. Cleaning and light oiling of the interior surfaces still matter, mainly for the steel bits and for keeping fouling from building into sludge. It makes sense to follow Sarco’s cleaning routine for the general process while staying conservative with chemicals. Use mild, aluminum‑safe solvents, wipe everything dry, and apply a light film on exposed steel areas rather than soaking the whole magazine.

For storage, you can treat aluminum magazines more like steel than like polymer. The AK‑style method of wrapping them in acid‑free paper, labeling, and then placing them in heavy zip bags with desiccant works equally well, and the same precaution applies: avoid direct metal‑to‑plastic contact in long‑term storage. In short, aluminum buys you some corrosion margin, but not enough that you can neglect oil and environment completely.

Polymer Magazines: Oil On Plastic And Hidden Steel Springs

Polymer magazines present a different set of tradeoffs. Primary Arms highlights them as the most popular choice today for good reason: they are lightweight, highly durable, and resistant to many environmental factors that attack steel and aluminum. Concerns that modern quality polymer feed lips deform badly under long‑term loaded storage are largely unsupported according to their guide, especially compared with older designs.

The catch is that you are dealing with two materials at once. The body and follower are polymer; the spring is still steel. Sarco’s maintenance guidance calls this out indirectly by warning that if you are working with a plastic magazine body you must use solvents and cleaners that are appropriate for plastic and will not damage it. Some aggressive solvents that are harmless on steel can soften or craze certain plastics, so generic “whatever is in the parts washer” is not always a good idea.

In terms of oil, the polymer body itself is not going to rust, so slathering it in oil is wasted effort and risk. The main corrosion targets remain the steel spring and any embedded steel components. Primary Arms points out that rust on springs is a genuine long‑term storage issue, even in polymer designs that look visually perfect from the outside.

The practical answer many experienced shooters settle on, consistent with the sources, is to keep polymer magazine bodies mostly dry and clean, while ensuring that springs and any exposed steel get enough protection for the environment they live in. For everyday use in relatively dry conditions, that might mean a thorough cleaning with a plastic‑safe solvent and no oil film at all on the spring, matching Sarco’s preference for a clean, dry spring inside a magazine that is not going into long, damp storage. In a coastal or high‑humidity environment, some shooters adopt the same light‑oil or storage‑grease strategies they use on steel mags, but keep that treatment targeted at springs and metal hardware, not at the polymer shell.

The bottom line is that polymer resists environmental attack well enough that oil becomes more about the hidden steel inside than about the outer shell. You gain a lot of corrosion resistance by material choice, but you do not completely escape the oil decisions.

Oil, Moisture, And Corrosion Science In Plain English

All of this magazine‑specific advice sits on the same physics that drives corrosion in much larger systems. Arizona State University researchers studying alloys for aerospace and defense underline that metal corrosion is a chemically driven decay process, driven by interactions with gases, liquids, salts, and temperature swings. National corrosion studies cited in defense‑oriented corrosion protection work put the annual U.S. cost of metal corrosion at hundreds of billions of dollars, on the order of a few percent of GDP. That sounds abstract until you realize that the same mechanisms eating bridges and aircraft are quietly working on your magazine springs and bodies every time moisture touches bare steel.

Corrosion specialists working on CO₂ pipelines and crude oil production emphasize three ideas that transfer well to magazines.

First, water contact time matters. In multiphase CO₂ pipelines, it is not just continuous water films that cause damage; even intermittent droplets that periodically wet steel surfaces can drive serious localized corrosion. Translated to gear, condensation in a safe, sweat moisture in an inside‑the‑waistband environment, or damp range conditions will add up if the metal is unprotected and stays water‑wet.

Second, surface wetting matters. Studies of crude‑oil chemistry and corrosion show that when natural organic compounds in the oil adsorb onto steel and make it more oil‑wet, corrosion often drops because water struggles to form continuous films. Your gun oil film is essentially a controlled version of the same thing. A proper, thin oil layer gives corrosive water fewer places to grab on.

Third, coatings and design choices pay off. Defense‑oriented corrosion guidance stresses environmentally friendly coatings, inhibitors, and good design as the most cost‑effective solutions. In the magazine world that is your choice of body material, any aftermarket coatings like NP3 on steel mags, and your procedure for applying and removing oil and grease so that they function as true protective films, not sludge traps.

Corrosion science does not say “more oil is always better.” It says “properly designed, continuous protective layers and reduced water contact are better.” That nuance is the difference between a magazine that looks greasy and still rusts in a damp bag, and one that stays reliable for years in a sealed, low‑humidity ammo can.

Long‑Term Storage: How Much Oil, What Wrap, Which Environment

When you shift from duty use to long‑term storage, the economics change. You care less about a tiny bit of extra drag from grease and more about whether your magazines emerge years later without pitting, frozen springs, or mystery rust blooms.

Primary Arms lays out a sensible storage hierarchy. For ordinary long‑term storage of “rainy day” mags, they recommend sealed containers such as MIL‑SPEC ammo cans or other moisture‑limiting boxes, combined with desiccants like silica gel to keep interior humidity low. Stored magazines do not need constant attention, but checking them every year or two and refreshing desiccant inserts keeps corrosion risk in check.

For very long‑term storage of steel magazines, they advise stepping up from oil to a light coating of grease on the springs and the entire exterior of the magazine body. Grease adheres better and offers stronger corrosion protection, particularly when the mags are not being cycled. The tradeoff is that this same grease has to be fully removed before the magazine goes into service, because it will otherwise attract dust, sand, and fouling.

The AK storage thread adds specific handling details that fill in the gaps. After cleaning and lightly oiling the magazine, the user wraps each one in acid‑free paper and tapes it closed. Acid‑free paper is chosen because it lacks acidic content that could contribute to long‑term corrosion of metal. The wrapped magazine is labeled with description, condition, and the date it was cleaned and wrapped, then placed into a heavy‑mil zip bag along with desiccant packs. The author strongly warns against metal directly contacting plastic during storage; the paper barrier is non‑negotiable.

Environmental control is the other half of the equation. Preservation guidance for paper collections from archival organizations like NEDCC and various magazine‑storage experts converges on a familiar climate profile: cool, dry, and stable. Typical recommendations for delicate paper items are temperatures around 60 to 70°F and relative humidity roughly in the 30 to 50 percent range, maintained without big daily swings. Metal is less sensitive to some of the chemical reactions that destroy paper, but corrosion behaves the same way. High humidity and temperature cycling accelerate attack; a cool, dry, steady environment slows it.

In practical terms, that means your worst storage locations are attics, garages, and damp basements. Attics experience extreme heat in summer and cold in winter; garages and cellars tend to be damp and more accessible to pests. Several storage guides for books and magazines also note that basements are prone to flooding and long periods of high humidity. Those same conditions will quietly chew on your magazine springs. A climate‑controlled storage unit or a controlled interior closet will always beat a sweaty, uninsulated outbuilding.

Put it all together and a value‑conscious long‑term storage recipe looks like this in practice. Clean the magazines thoroughly. Apply an appropriate level of oil or grease based on how long you expect them to sit and what they are made from. Wrap metal magazines in acid‑free paper, add desiccant, and seal them in robust containers. Store those containers in a cool, dry location, not in a damp garage or baking attic. Label everything with dates so you know when it was last serviced. You are buying time and certainty cheaply compared with replacing corroded gear under a future magazine‑capacity ban.

Everyday Use: Running Mags Wet Enough To Survive, Dry Enough To Run

Daily carry and training magazines have a different mission. They see more dirt, more impacts, and more cleaning cycles than anything locked in a can. For these, reliability today matters more than fifteen‑year cosmetic perfection.

Sarco’s rifle magazine guidance falls squarely in this camp. They describe magazines as vital to the firearm’s function and warn that fouling, grime, oil, dust, and dirt will work their way into the magazine body over time, causing seating and feeding issues and accelerating corrosion on the springs. Their cleaning routine ends with a very thin protectant layer on the body and follower, not on the spring, and a strong warning against over‑oiling because it attracts contamination.

Primary & Secondary contributors focusing on metal pistol magazine corrosion prevention approach maintenance in tiers. For mild surface discoloration or stable “patina” on older mags, they may simply keep the magazines lightly oiled and in service, treating that brown film as cosmetic rather than as active rust. For magazines that have bare or worn spots, they suggest more intensive home repair: full disassembly, cleaning, rust converter on affected areas, then a very light coat of good‑quality spray paint as a protective finish. For heavy use or high‑value mags, they even mention sending them to professional refinishers for coatings such as NP3, accepting higher coating cost in return for more durable corrosion resistance.

SIG Talk users, looking at rust issues aggravated by plastic bags and temperature swings, point out another everyday reality: people get lax about maintenance because of modern stainless and rust‑resistant finishes. Their simple fix is regular wipes with a silicone cloth and considering pocket magazine covers that physically shield mags from lint and pocket junk. None of this is glamorous, but it is cheap and effective.

Primary Arms adds another operational point that matters when you are trying to build a sustainable routine. They argue against constantly “rotating” magazines in the belief that springs need to “rest.” Modern magazine springs primarily wear from compression cycles, not from being held compressed. Unloading and reloading repeatedly does more harm than letting a magazine sit loaded. For shooters on a budget, that means it is smarter to buy a reasonable pool of good magazines, keep the ones you rely on clean and properly protected, and leave them largely undisturbed between periodic inspections rather than constantly cycling them.

For duty and training use, a practical rule emerges from these sources. Clean and inspect your magazines whenever you clean the gun. Run them with surfaces just oily enough to ward off rust in your environment, and no wetter. Keep springs clean and dry unless you are deliberately preparing for harsh, high‑humidity storage. When in doubt, err on the side of less oil for carry mags and more environmental control.

Common Mistakes And How To Avoid Them

Most magazine and oil problems come from a handful of predictable mistakes.

One mistake is drowning steel magazines in oil, then dropping them into unvented plastic bags or pouches. The AK storage thread explains why that is a bad pairing: plastic can trap moisture and off‑gassing against the metal, and heavy oil films hold that moisture in place. Without a paper barrier and some humidity control, you have built a corrosion cell, not a protection system.

Another mistake is ignoring hidden rust on springs inside polymer or aluminum magazines. Primary Arms stresses that rusted springs are the main long‑term threat to stored magazines, regardless of body material. If your maintenance routine never includes disassembly and inspection, you will miss pitting or discoloration on springs until you start seeing unexplained feeding issues.

A third mistake is trusting general gun solvents and aerosols around polymer without checking compatibility. Sarco explicitly notes that you should use a solvent or cleaner that is safe for plastic if you are working on polymer magazines. That warning exists because some chemicals that are fine on steel can damage certain plastics. The safest pattern is to choose cleaners known to be plastic‑safe and avoid long soak times on polymer components.

A fourth mistake is mistaking discoloration for fatal rust or, in the opposite direction, treating active rust as harmless “patina.” The Primary & Secondary conversation around metal pistol magazines recognizes that older mags often develop a brown patina that is stable and not actively worsening. That is not the same as flaky, active rust that lifts and undercuts finishes. Learning to distinguish between the two, and backing that with occasional detailed cleaning and inspection, keeps you from discarding serviceable mags or trusting compromised ones.

Finally, over‑handling stored magazines in the name of “rotation” accelerates wear without adding reliability. The Primary Arms guide is clear that modern springs wear primarily from cycles, not static compression. Every time you unload and reload a magazine just to feel like you are “doing something,” you are putting unnecessary cycles on the spring and adding more opportunities for dirt and fingerprints without tangible gain.

Avoiding these traps costs almost nothing. It simply demands that you respect the interaction between oil, material, and environment instead of treating oil as a cure‑all.

Quick Material And Oil Reference

You can use this table as a snapshot of how oil interacts with different magazine materials, based on the sources discussed.

Magazine material	Key traits from sources	Oil and protection role	Typical problems if misused
Steel bodies with steel springs	Toughest and often repairable; most susceptible to rust; best in dry climates; common on AK and surplus platforms	Thin oil film or storage grease acts as primary corrosion barrier; wrapping in acid‑free paper and using desiccant for long storage adds major protection	Heavy oil in sealed plastic traps moisture; lack of barrier to plastic accelerates corrosion; thick grease left in service attracts fouling and slows followers
Aluminum bodies with steel springs	Lightweight, corrosion‑resistant body; feed lips and body prone to dents and bending; springs still vulnerable	Light oil film protects exposed steel and interfaces; aluminum body needs less rust‑proofing but still benefits from cleanliness and mild protection	Over‑aggressive solvents or neglect of springs; relying on “aluminum does not rust” and ignoring interior corrosion; dented feed lips causing misfeeds
Polymer bodies with steel springs	Very light, durable, and widely used; resistant to many environmental factors; cracked bodies not practically repairable	Body itself does not rust, so oil focus shifts to springs and steel hardware; cleaning with plastic‑safe solvents prevents chemical damage	Using harsh solvents not compatible with polymer; ignoring rust on internal springs because exterior looks fine; over‑oiling interior and turning dust into sludge

This is where value and practicality intersect. If you understand which part of each magazine type actually needs protection and how oil interacts with that material, you can put your maintenance time and budget exactly where it pays off.

Short FAQ

Should I oil my magazine springs?

The sources do not agree on a single universal rule, and context matters. Sarco’s rifle magazine guide prefers springs that are thoroughly cleaned and completely dry before reassembly, to avoid attracting dirt and forming sludge. Primary Arms, looking at very long‑term storage, is comfortable with a light grease coating on springs in steel magazines stored in sealed, low‑humidity containers, as long as that grease is removed before they go back into service. A conservative approach is to keep everyday‑use springs clean and dry, and reserve light oil or grease on springs for long‑term storage in controlled environments where you can degrease before use.

Do I need to rotate my loaded magazines so the springs can “rest”?

Primary Arms makes it clear that modern quality springs primarily wear from compression cycles, not from being left compressed. Frequently unloading and reloading magazines to “rest” them actually adds wear instead of preventing it. For most shooters, it is better to load good magazines, store them in a dry, controlled environment, and check them periodically than to constantly rotate them without a plan.

Closing

Magazines are where your rifle or pistol succeeds or fails. Ammunition oil and gun lubricants are not magic in that system; they are tools that can either extend magazine life or quietly sabotage it, depending on how they interact with steel, aluminum, and polymer in your specific environment. If you treat oil as a deliberate barrier against corrosion rather than a universal cure, match it to your magazine material, and store your gear in conditions that make sense, you will get more reliable years out of the magazines you already own and spend less money fixing preventable problems.

Understanding How Ammunition Oil Affects Your Magazine Material