Though not common today, the 5.45x39mm AR-15 was popular for a time. There are still a fair number of these guns in circulation but they are something of a novelty today.
Why the 5.45x39mm?
The USSR issued the 7.62×39 round in the AK-47, AKM, RPK, and others, but there was a desire for a small diameter, high velocity round. The M-16 had popularized the idea of light and fast bullets in assault rifles and the Soviets decided to make their own. The 5.45×39 was the result of that movement.
The cartridge saw its first real use in Afghanistan. It was famously known as the “Poison Bullet” among the Mujahideen for the unique wound track and violent tumbling. Entrance wounds were typically a small diameter hole, but internal damage to the target was often extreme. The design of the standard “7n6” loading utilized a copper jacket with an enclosed air pocket in front of the steel penetrator and lead core.
Cheap Russian surplus ammo flooded into the US market after the end of the Cold War. The most common loading was the 7n6, which had a 53-grain projectile with a mild steel core and a hollow cavity inside the jacket. The ammunition came in a crate containing two “spam” cans, each containing 1080 rounds broken up into 30 round paper packets.
Importation of 7n6 ammunition was banned by the ATF in 2014, on the basis that it was armor piercing handgun ammunition. Commercial steel-case loadings are still available from Hornady, Red Army Standard, Silver Bear, Tula, Wolf, and others. These loadings are largely comparable, with the exception of the Hornady load with a V-Max projectile.
How Does That Work in an AR-15?
The AR is ubiquitous in the United States, and it was only a matter of time before someone figured out a way to use the plentiful, cheap 5.45x39mm ammo. Any standard AR-15 can be converted to 5.45 with the change of a barrel and bolt. However, a heavy trigger spring and improved firing pin are strongly recommended due to the hard primers on imported ammunition. Standard 5.56 magazines can be used but dedicated steel 5.45 magazines from ASC or C-Products (now known as Duramag) provide greater capacity.
Accuracy with the 5.45 is decent, but you should not expect match-grade accuracy with the surplus ammunition. Commercial offerings, especially the Hornady V-Max load, perform better. I have not yet tried reloading for the cartridge but Hornady recently introduced brass cases and properly-sized projectiles so that is now a possibility.
My 5.45x39mm AR-15s
During the 2013 panic, I found a Smith & Wesson M&P-15R in 5.45×39 at a local gun store. It was the only AR on the wall. I already had access to surplus ammo, and the rifle ended up coming home with me. The M&P-15R was a short lived model which was discontinued when the cheap ammunition dried up. The rifle was designed around the 5.45, and included a chrome-lined barrel to deal with corrosive surplus ammunition, as well as the optimized hammer spring and firing pin.
Over the years this rifle has had various changes. It is currently equipped with a Magpul SL-K stock and SL grip, Viking Tactics sling, SilencerCo ASR muzzle brake, Magpul AFG, Troy Industries fixed rear sight and handguard, Magpul BAD lever, a flashlight, and Vortex Sparc red dot. At its core, this is still a fairly standard AR-15 with a carbine gas system, 16″ barrel, and carbine buffer tube.
One upgrade not visible from the outside is the bolt carrier. The M&P-15R shipped with an AR-15 carrier which I swapped to an M-16 carrier. Changing out the bolt carrier made this upper compatible with machine gun lower receivers. Performance on full auto is excellent. The 5.45 is a low recoil cartridge, and on a post-sample SOLGW lower the rate of fire was fast but manageable.
Corrosive surplus ammunition can damage a gun if not properly cleaned. Fortunately, the corrosive salts are easily cleaned out with water. When I finish shooting for the day, I pour water down the barrel and gas tube. This works best with a gun that is still hot from shooting, as that aids in evaporation. Once the gun is dry I apply oil and clean it as normal.
My second 5.45×39 AR-15 was a parts build. An Instagram friend had converted a customer’s M&P-15R to 5.56, and was left with a spare bolt and barrel. He made me a deal and those parts sparked yet another AR build, as spare AR parts have a tendency to do. This gun was built on a blemished A2 upper receiver covered with pink speckles, a hideous green anodized Bushmaster lower, and various spare and take-off parts in my parts bin. The ugly nature of the parts made this an obvious candidate for a spray paint job.
I am not aware of any current production 5.45×39 AR-15 options, but parts kits may still be available. Ammunition in just about any caliber is hard to find these days. If you happen across a good stash of 5.45×39 ammunition and are looking for a way to use it up, you may be able to find a used AR. Unlike the various AK options on the market, your new-to-you-but-old AR can be swapped out to 5.56×45 once your ammo supply dries up.
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