Editing AK-47 (section)

===Further development===
[[File:AKMS and AK-47 DD-ST-85-01270.jpg|thumb|AKMS with a stamped Type 4B receiver (top) and an AK-47 with a milled Type 2A receiver]]
There were many difficulties during the initial phase of production. The first production models had [[Stamping (metalworking)|stamped]] sheet metal receivers with a [[Milling (machining)|milled]] [[trunnion]] and butt stock insert and a stamped body. Difficulties were encountered in welding the guide and ejector rails, causing high rejection rates.{{sfn|Poyer|2006|pp=8–11}} Instead of halting production, a heavy<ref group=N>2.6 lb milled from 6 lb stock. This was about 2.2 lb heavier than the stamped receiver.</ref> machined receiver was substituted for the sheet metal receiver. Even though production of these milled rifles started in 1951, they were officially referred to as AK-49, based on the date their development started, but they are widely known in the collectors' and current commercial market as "Type 2 AK-47".<ref name="e36" /><ref name="ForgottenWeapons.com" /> This was a more costly process, but the use of machined receivers accelerated production as tooling and labor for the earlier Mosin–Nagant rifle's machined receiver were easily adapted.<ref name="browningmgs.com" /> Partly because of these problems, the Soviets were not able to distribute large numbers of the new rifles to soldiers until 1956. During this time, production of the interim SKS rifle continued.{{sfn|Poyer|2006|pp=8–11}}

Once the manufacturing difficulties of non-milled receivers had been overcome, a redesigned version designated the AKM (M for "modernized" or "upgraded"; in Russian: {{Lang|ru|Автомат Калашникова Модернизированный|italic=no}} [{{Lang|ru-latn|Avtomat Kalashnikova Modernizirovanniy}}]) was introduced in 1959.<ref name="e36" /> This new model used a stamped sheet metal receiver and featured a slanted [[muzzle brake]] on the end of the [[gun barrel|barrel]] to compensate for [[muzzle rise]] under recoil. In addition, a hammer retarder was added to prevent the weapon from firing out of battery (without the bolt being fully closed), during rapid or fully automatic fire.{{sfn|Poyer|2006|pp=8–11}} This is also sometimes referred to as a "cyclic rate reducer", or simply "rate reducer", as it also has the effect of reducing the number of rounds fired per minute during fully automatic fire. The rifle was also roughly one-third lighter than the previous model.<ref name="e36" />

{| class="wikitable" style="text-align:left; margin:auto;"
|-
! Receiver type
! Description<ref name="browningmgs.com" />
|-
! Type 1A/B
| The original [[Stamping (metalworking)|stamped]] receiver for the AK-47 was first produced in 1948<ref name="Ezell, Edward Clinton 1986 112"/> and adopted in 1949. The 1B was modified for an underfolding stock with a large hole present on each side to accommodate the hardware for the under folding stock.
|-
! Type 2A/B
| The first [[Milling (machining)|milled]] receiver was made from steel forging. It went into production in 1951 and production ended in 1957. The Type 2A has a distinctive socketed metal "boot" connecting the butt stock to the receiver and the milled lightning cut on the sides runs parallel to the barrel.
|-
! Type 3A/B
| "Final" version of the AK milled receiver made from steel bar stock. It went into production in 1955. The most ubiquitous example of the AK milled receiver. The milled lightning cut on the sides is slanted to the barrel axis.
|-
! Type 4A/B
| AKM receiver stamped from a smooth {{convert|1.0|mm|abbr=on|2}} [[Sheet metal|sheet]] of [[steel]] supported extensively by pins and rivets. It went into production in 1959. Overall, the most-used design in the construction of AK-series rifles.
|}

Most licensed and unlicensed productions of the Kalashnikov assault rifle abroad were of the AKM variant, partially due to the much easier production of the stamped receiver. This model is the most commonly encountered, having been produced in much greater quantities. All rifles based on the Kalashnikov design are often colloquially referred to as "AK-47s" in the West and some parts of Asia, although this is only correct when applied to rifles based on the original three receiver types.{{sfn|Poyer|2006|p=2}} In most former Eastern Bloc countries, the weapon is known simply as the "Kalashnikov" or "AK". The differences between the milled and stamped receivers includes the use of rivets rather than welds on the stamped receiver, as well as the placement of a small dimple above the magazine well for stabilization of the magazine.