The G36 and the M4 are both popular and widely used firearms, but they have some notable differences. Let's compare them:

Design and Origin:
G36: The G36 is a modular assault rifle developed by the German company Heckler & Koch (H&K). It was designed in the 1990s as a replacement for the aging G3 rifle used by the German military.
M4: The M4 Carbine is a shorter and lighter variant of the M16 rifle. It was developed by the American company Colt's Manufacturing Company and is based on the AR-15 platform.

Caliber:
G36: The G36 fires the 5.56x45mm NATO cartridge, the same as the M4. It is a standard intermediate cartridge used by many NATO forces.
M4: The M4 also fires the 5.56x45mm NATO cartridge. This caliber offers a balance between recoil, range, and lethality.

Operating System:
G36: The G36 uses a gas-operated, rotating bolt system. It features a piston-driven operating system, where gas is tapped from the barrel to drive the piston, which then cycles the action.
M4: The M4 uses a gas-operated, direct impingement system. It does not have a piston and instead uses the gas pressure to directly cycle the action.

Construction:
G36: The G36 has a polymer frame, which helps to reduce weight while maintaining durability. It has a folding stock and a modular design that allows for easy configuration changes.
M4: The M4 has a mostly metal construction with a lightweight aluminum receiver. It typically has a collapsible stock for improved portability and adaptability.

Accessories and Customization:
G36: The G36 has a built-in optic and a carrying handle with integrated iron sights. It also features a Picatinny rail on the top of the receiver for mounting additional accessories.
M4: The M4 often comes with a detachable carrying handle or a flat-top upper receiver with a Picatinny rail for attaching optics, sights, and other accessories. It offers a wide range of customization options and aftermarket accessories.

Overall Performance and Ergonomics:
G36: The G36 is known for its reliability and accuracy. Its ergonomics are designed for ease of use and handling. The polymer construction helps to reduce weight, making it a maneuverable firearm.
M4: The M4 is also reliable and accurate. Its shorter barrel makes it more suitable for close quarters combat, and its collapsible stock allows for better handling in tight spaces. It has a well-established track record and is widely used by the U.S. military.

Both the G36 and the M4 have their own strengths and have been adopted by various military and law enforcement organizations worldwide. The choice between them often depends on specific requirements, preferences, and operational needs.