There are three basic types of Kalashnikov rifles on the market. They are the AK47, AKM47, and the RPK (heavy duty receiver). As most of you know, the AK47 was designed as an infantry rifle capable of firing in either the semi-automatic or fully-automatic mode.
The first AK47s had machined receivers. Later the Soviets produced the AKM47s (the "M" stands for modern), the Soviets found that stampings were not only more efficient to produce but resulted in longer receiver life and better accuracy than the milled receivers.
The RPK, on the other hand, was designed as, what we would refer to as a squad automatic weapon. The RPK could also be fired in either the semi or fully-automatic modes. Squad automatic weapons, as deployed, are more frequently fired in the fully automatic mode. For this reason, one usually sees the RPK pictured with an ultra-high capacity magazine such as a 75 round drum or 40 round box magazine instead of the standard 30 round magazine typically used with the AK.
To handle the sustained automatic fire, the RPK was designed to be much stronger. First, the sheet metal of the receiver of the RPK is 50% thicker than that of the AKM47. Next, the trunion of the RPK is larger and stronger than that of the AK47 or AKM47. The trunion is the part to which the barrel is connected and into which the bolt locks. Because the trunion is larger, the receiver must be bulged out to accept the larger trunion. Hence the above mentioned bulges on the RPK receiver.
Most of the MAK90s, WUMs, Maddis, MISR, etc. are semi-automatic sporting rifles based on the AKM47. On the other hand, the VEPR is based on the RPK. This stiffer receiver makes for better accuracy and longer life. This is why the VEPR is a better rifle than the those based on the AK.
The VEPR costs more for a reason - It is simply the finest Kalashnikov based rifle available in the U.S. market.
