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Should I Buy BiMetal Ammo?
by: Story, Research, and imagery by Eric Jay Miller, Northwestern University Electron Probe Instrumentation Center (EPIC)

Should I Buy Bimetal?
Story, Research, and imagery by Eric Jay Miller, Northwestern University Electron Probe Instrumentation Center (EPIC)
Like many Americans searching for a solid handgun for concealed carry, my attention was drawn to surplus military pistols from Cold War Eastern Europe. They're inexpensive and fire the medium powered 9x18mm Makarov round, which is a bit more powerful than the common .380ACP (aka 9x17mm). But, once I had purchased a Makarov-caliber pistol, I found myself unwittingly sucked into the dread debate over "Steel Core Ammo!"

 Before you stop reading I want to let you know that this is not an article about the 9x18mm round. Our subject today is bimetal jackets. The 9x18mm makes a good example because so much 9x18 ammunition imported into the United States today is bimetal, and "bimetal" is often confused with "steel core". Also, before I get too far and someone has a meltdown, I want to make it clear that we are talking about steel in bullets and NOT about steel cases. That is a different issue altogether.

 Confusion over the issues of "bimetal" versus "steel core" ammo has a great deal of significance for rifle and pistol shooters because many ranges ban any bullet that responds to a magnet - especially  indoor ranges with steel backstops. I've even heard of one range that banned any pistol chambered in 9x18mm Makarov! Why is this medium-strength pistol round so despised by range owners? It's the "bimetal" ammunition. The steel in the projectiles chews up steel backstops.

 I found this out the hard way when I took my new CZ-82 to the indoor range with the only 9x18mm ammo I could get: Norinco FMJ, Brown Bear FMJ and Silver Bear JHP (the Bear ammo stated "bimetal" on the box). When I entered, the sign on the door said: "No Wolf Ammo." I thought about it for a second and decided, 'I don't have any Wolf ammo, so I should be fine.' After my bullets caused some sparking off the steel backstops and some suspicious looks by the range staff, the sign at that range now reads: "No Bimetal Ammo." In the past this issue has been mostly isolated to common Russian calibers such as 9x18mm and 7.62x25mm. Today, however, more bimetal alternatives are being imported by manufacturers such as Wolf, Herter's, Tulammo, Ulyanovsk, and Barnaul (which makes Brown Bear and Silver Bear) to name a few.

 To help prevent more unwitting shooters from getting yelled at by range owners, I decided to look a little closer at this "bimetal" ammo. When I did, a number of things about it confused me. First, what are these two mystery metals in "bi" metal ammo? (After all, aren't all jacketed bullets technically bimetal? i.e., copper and lead?) The bimetal bullets are supposed to have steel in them somewhere, and the jackets are a copper color, so what's the deal? Where is the lead? Where is the steel? I was perplexed, so I needed to take it to the next level.

 In my position as the Microscopy and Imaging Specialist at the Electron Probe Instrumentation Center (EPIC) at Northwestern University, I have access to an amazing array of electron microscopes and related instrumentation.

 I took a sampling of bullets from different manufacturers (Wolf, Herter's, Brown Bear, Norinco), sectioned them (cut in half), and polished them. I took the polished cross-section samples and put them in a Scanning Electron Microscope (SEM) and performed Energy Dispersive X-Ray Analysis (EDX) on them. What in Fraggle Rock does that mean? To put it briefly, EDX tells you what elements are present in your sample. I was then able to take that information and make a map of where each element is located on the sample. This enabled me to divine the answers to many of my bimetal related questions, the reality of which will shock you!

 OK, it's really not that shocking. The bullets turned out to be lead-cored, but steel jacketed, with a very thin copper coating over the steel. So, the term bimetal refers only to the jacket and not the bullet as a whole. How thin is this copper coating, you ask? Very thin. I measured five different bimetal rounds and the outer copper coating was only about 20-30 micrometers (abbreviated µm). How small is that? Well, there are 1,000µm in a millimeter and the hairs on your head range from around 50-100µm thick.

 Discovering these simple facts makes the whole thing come together for me. If you wanted to make a regular copper-jacketed lead bullet cheaper, you would look first at eliminating or at least diminishing the more expensive of your two materials, in this case copper. One of the ways some manufacturers achieve this today is by using a brass jacket instead of a pure copper one. For example, Sellier & Bellot makes most of their jackets out of "cartridge brass" which is 70% copper / 30% zinc. It's still mostly copper, but less copper means cheaper bullets. BUT, let's say you really wanted to put your bullets on a copper crash diet. Steel is an attractive alternative…at first glance. It's cheap, plentiful and easy to work with. The obvious problem with using steel as a jacket material is that it would in all likelihood wear a barrel's rifling at a much faster rate than copper or brass. Besides, who on earth would buy ammo labeled as "Steel-Jacketed?" I'll tell you who: A crazy person who wants to destroy the rifling in their gun! So, if you're going to make steel-jacketed ammo, you need to place a cushion between the steels of the jacket and the barrel. Something like copper, perhaps. Fortuitously, a thin copper coating would also work double duty by helping to protect the steel from corrosion.
 Knowing now that we are not in actuality dealing with "steel-core" pistol ammo, does such a thing actually exist?


 I've read that Omnishock makes a .38 Special round with a steel core and at least one Czech and one German manufacturer make it in 9x19mm. I say I've only read about the pistol rounds because it's unlikely you'll see any of it here in the United States. The Federal government has put restrictions on handgun ammunition that has a hardened core (or with a jacket that weighs more than 25% of the total bullet) as it's considered to be armor piercing (AP). These restrictions don't make it illegal to own, use or sell, it's just illegal to make it or import it.

 These restrictions however, do not extend to steel-core rifle ammunition, which is uncommon, but hardly rare. The Army's well-known SS109 bullet for the 5.56 NATO round contains a steel penetrator (like a tiny nail inside the bullet), as do other military rifle rounds.  The SS109 is available over the counter in the United States, probably as close as your local gun show. Several states restrict steel-core, but most outdoor ranges ban steel-core rifle ammunition outright. The reason for this is due to the possibility of the steel in the round sparking off a rock and starting a fire, or drilling into steel backstops and targets. Based on the fire danger (which sounds plausible enough to me), I think a good case can be made by a range owner to ban bimetal ammo from their outdoor ranges as well. Steel core is not the same thing as a copper-coated steel jacket ("bimetal"), but as far as fires go, there is a potential risk.

 How then, does one avoid being chased out of their local range by accidentally shooting bimetal ammo? Surely, you can just read the box, right? Certainly some brands, like Tulamo and Barnaul, state "Bimetal" on their packaging. Unfortunately there are others, like Wolf and Herter's, which do not. The only thing in common I could find to all bimetal ammo is that they are imported from Russia or China (though China hasn't been allowed to import ammo to the United States since 1994). The difficulty here lies in the fact that NOT ALL ammo from Russia is bimetal. Wolf, Barnaul and Herter's, for example, all offer a line of ammo which consists of copper or brass jackets with no steel.

 So how do I know for sure if my ammo has a steel jacket? Do as the 3-Gunners do, and get a magnet! Three-gun matches around the United States often forbid the use of any ammunition that responds to a magnet. Steel core, or steel jacket, they don't care. If the bullet sticks to a magnet, you can't use it. When you're checking this, remember that most - but not all - bimetal ammunition has a steel case. The point is, when you check your ammo with a magnet make sure the pull you're experiencing is definitely coming from the bullet and not tangentially from the steel case. The other option you can try, if you don't have a magnet, is sandpaper. The copper coating on bimetal jackets is extremely thin. If it's present, a couple swipes across the surface of the bullet with some sandpaper should reveal the dark silver color of the steel.

Okay, I've Got BiMetal Ammo, Is It Safe For My Gun?
 The big question that we're left with after discovering the actual composition of these bullets is: will shooting this stuff hurt my gun? There are many people out there who will tell you that Wolf ammo (for example) will destroy your gun. The original reason I heard for this was because it was somehow extra-powerful. That explanation didn't make sense to me since I've seen data from more than one source that shows Wolf ammo moving at about the same speed as other ammo. So how can a standard weight bullet traveling at a standard velocity be perceived as "too powerful?" Well, if that bullet had an unseen steel jacket and was damaging your range's steel targets and backstops, that would be an understandable conclusion. While I suspect the bimetal jacket might have contributed to Wolf's fearsome reputation (ignoring the steel cases), is there any potential for the steel in the jacket to cause gun damage?

 I believe the possibility exists. To divine this, I took a Polish P-64 (9x18mm) and a Hi-Point C9 (9x19mm) with me to the local indoor range along with some copper and bimetal jacketed ammo in both of the respective calibers. Using these two guns, I shot the ammo into a 2-foot thick stack of wet newspaper. The fired bullets were then able to be recovered wholly intact. I then cross-sectioned the fired bullets, polished them and put them in the SEM and fired up the EDX.

 I started by looking at the cross sections of the "normal" copper jacketed bullets I had fired and it appeared that the rifling from my C9 was penetrating about 40µm into the jacket. I knew right off the bat this would be bad news for the Herter's bimetal bullets I had used for this test since their copper coating was only about 15-20µm. Indeed, when I put the cross-sectioned Herter's bullet into the microscope, the x-ray analysis told the story. In clear detail the images showed that when a bimetal bullet is fired, the rifling of the barrel DOES penetrate the thin copper coating over the steel jacket.

 Just looking at the cross sections, I wasn't so sure how bad this was. So I put a whole bullet fired from each of my guns into the SEM to see if the copper was really stripped away and the steel was showing through. The answer to both questions was YES. The 9x19mm Herter's bullets fired from my C9 showed a long trench of exposed steel down the length of each of the rifling striations. The 9x18mm Barnaul bullets fired from my P-64 were not quite as orderly, but they had numerous areas of exposed steel across their surface.

 Now, the rifling was not penetrating the steel jacket as deep as I thought it might, but that's not important. What is important is that it IS happening. The problem we're left with is: How bad is it for your gun to fire a piece of steel out of it? Unfortunately I have no way quantifying how bad it might or might not be at this time. However, we do know that copper is a soft material, which is why it's used as a jacket material. Brass is a bit less soft than copper, which is why we use it for cleaning brushes. On the other hand, carbon steel is very difficult to describe as soft, and stainless steel cleaning brushes come with warnings. The hardness of different steels vary quite a bit, but given a choice between something made from copper or brass and something steel, I can tell you which I would prefer to have scraping along the rifling of my gun's barrel at 1,000 feet per second. (I'll give you a hint, it's not the steel.)

 Eric Jay Miller is a Microscopy and Imaging Specialist under Prof. Vinayak P. Dravid at the Electron Probe Instrumentation Center (EPIC). EPIC is part of the Materials Research Science and Engineering Center (MRSEC) at Northwestern University, housing one of the most complete arsenals of electron microscopes in the world. www.nuance. northwest
 Thanks to Stephen A. Camp from for advice on techniques to recover fired bullets intact.

 Special thanks to Maxon Shooters Supplies and Indoor Range for letting me in to do my crazy tests.


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