Brass Fetcher Ballistic Testing
The 5.45x39mm cartridge is the Soviet Unions response to the 5.56x45mm NATO cartridge. Projectiles launched by the more common 7.62x39mm typically do not tumble early enough in the penetration track for maximum effectiveness. The 5.45x39mm cartridge changes all of this with a bullet length-to-diameter ratio of 4.3:1 while the 7.62x39mm bullet length-to-diameter ratio is 3.1:1. Small changes in bullet configuration can make large differences in terminal performance. People as historically familiar with hardship as can be found in Russia and the Former Soviet Union states don’t waste anything and do not delay to take action when action is needed. The redesign of the 7.62x39mm round to create the 5.45x39mm was not an accident and it surely serves some new and important purpose that the older cartridge cannot. A vital area hit from an AK47 is a serious wound when ball ammunition is used … it is almost certainly life-threatening when an AK74 hit with ball ammunition occurs. Let’s take a brief look at the differences in penetration depth before tumble of four familiar bullet types (5.45x39mm, 7.62x39mm, 5.56x45mm and 7.62x51mm FMJs):
Examples of this function are represented graphically below.
It is typical for bullets with higher length-to-diameter ratios to be less stable in flight which translates to less stability in tissue. The less stable a bullet is, the more likely it is to tumble early in the penetration track. A bullet is more effective the greater the surface area it exposes to the oncoming rush of tissue or ballistic gelatin. This increases the fluid drag which increases the trauma done by the bullet to the tissue.
Speaking generally, all 5.45x39mm FMJs should be able to perform similarly to the 7N6 though I highly recommend that you obtain some military surplus ammunition when available. The odds are very good that the round, through shear luck and unintentionally, is optimized for self-defense type shooting. One factor that makes a FMJ tumble early is a weight concentration to the rear of the bullet. The air space that is present at the tip area of some bullets helps to push the center of mass of the bullet towards the base which creates instability at the nose when the bullet encounters significant fluid resistance. If the bullet has a slender nose and is long, there is a fair bet that it will tumble early enough in the track to be effective.
The 5.45x39mm cartridge is ballistically similar to the 223 Remington and 5.56x45mm cartridges so a good softpoint will allow this cartridge to be useful for hunting small game. A good softpoint is hard to find. You need to shoot a few different types of softpoint ammunition into a tissue simulant and examine the recovered bullets for fragmentation. If the bullets hold together well enough to penetrate to 12.0” of 10% ballistic gelatin, then you have a viable softpoint for self-defense. The military FMJs are also very good. So the question is: what might make the difference in the softpoint vs FMJ decision process? In a word: price. You will want to use the same ammunition type and lot in all of your magazines if you expect to maintain the same correlation between point of aim and point of impact. A typical chest-type magazine pouch will carry 6 30-round magazines. If those magazines are loaded with $1-a-round ammunition, you are carrying around at least $180 in ammunition in your vest. While I salute anyone who takes their ammunition selection seriously as a part of being prepared, it may be comforting to realize that most shots fired during emergencies miss. This means that cheaper ammunition that has acceptable terminal performance may be a better buy overall than premium ammunition for this application.
Armor penetrating ammunition is available for the 5.45x39mm in some localities. If you are legally able to purchase armor piercing ammunition for your firearm, I strongly recommend it from a technical standpoint. The 5.45mm, along with all of the other intermediate caliber cartridges, will not penetrate a concrete wall with lead core ammunition. You have the possibility of penetrating this cover when using AP ammunition though the terminal effect on the target behind the wall will be lacking.