Implementations of a rear sight block for AK-type rifles are provided. In some implementations, the rear sight block may be drop-in-compatible with most AK-type rifles and performs several functions (e.g., providing a guide hole for the piston of an AK-type rifles operating system) associated with prior art rear sight blocks found on AK-type rifles. In some implementations, the rear sight block disclosed herein comprises an optic mounting interface having an integral rear sight notch therein, and at least one accessory mounting interface. In some implementations, the optic mounting interface places an optical gun sight secured thereto in line with the iron sights of the host AK-type rifle. In some implementations, the accessory mounting interface may be used to position a flashlight, laser, and/or other firearm accessory on the left (or right) side of the rear sight block.