The design of an AK is pretty simple and does not represent a huge technological breakthrough in firearm technology. But how they work together to produce the desired result is what really mattered in the creation of Mikhail Kalashnikov’s masterpiece.
This inherent reliability was achieved by the spacing of the components, with a receiver allowing the contaminants to “fall” though the gun or accumulate for some time before they started to impede the normal operation of the gun. Utter simplicity of operation was also a main goal, and it was achieved by mimicking a conventional rifle configuration, which made it easy to re-train existing soldiers and train new recruits on a rifle that can be mastered within days.
The AK operating system is based on a long-stroke gas piston driven back by the powder gases compressing the main recoil spring that in turn feeds the round out of a box-type magazine, chambering it and locking a two-lug bolt. The AK bolt locking is achieved by rotation, unlike in the Stg .44, which used tilting. The guide rails on the inside of the receiver enable the rotation of the bolt within a bolt carrier.
The hammer-forged barrel with four right-hand grooves at a 240mm or 1-in-9.45 inch rifling twist rate and chrome-lined bore is pressed into the front trunnion block. Most of the commercial models that are imported into the US from Russia have chrome-lined military-spec barrels. The same could be said for European models, depending on the country of origin. Most of the US-made AK barrels are not chrome-lined; however, other forms of corrosion prevention are employed. The barrel has a gas port drilled in the top to align with a gas block that is pressed on and pinned in place. The original design had a 45-degrees port to vent powder gases to cycle the rifle.
Originally, on the first model of the AK-47 the hood had a tube shape to enclose the sight post entirely, with an opening on top to allow for elevation adjustment. Later models up to this day have a “U” shaped hood that was first employed by the Soviets in the '50s as part of modernizing the AK rifle. This move made casting simpler and eliminated two milling steps to make the process cheaper.
The sighting system for the AK was borrowed from the standard military two-sight alignment system where the elevation-adjustable “U” shaped rear sight is aligned around the “fixed” front sight. The leaf spring-tensioned rear sight is hinged on the top of the “rear sight” block, and it has graduations from 1-10 in single-digit increments representing 100 meters. i.e. 1-100 meters and 10-1000 meters.
When the AK-47 was first adapted for service with the Soviet Armed Forces it had furniture made of hardwood, but cost-cutting measures switched that to birch laminate. This move achieved a double benefit: It was much cheaper because the material was plentiful, and it was much more rigid and could withstand more abuse. Advances in plywood production allowed for an infinite supply of components, as it did not require a careful selection for the wood used.
Later attempts were made to replace all of the rifle’s wood furniture with composite parts. Early Bakelite technology was widely employed throughout the firearms industry, and the Soviets jumped on the Bakelite bandwagon as well. However, Bakelite proved to be an excellent heat conductor and was abandoned in favor of laminate wood, with the exception of the pistol grip and bayonet handles and scabbard.
Finally, in the early '80s, the first AK-74 had its furniture replaced with “plum” colored glass-filled plastic, and not before 1990 would the first all-black plastic-clad AKs appear, and in the process giving the AK more of a modern look. The majority of the Kalashnikovs built in the US now have some sort of black polymer furniture.
This article is an excerpt from Gun Digest Shooter's Guide to AKs (edited for length).