The CETME C308, HK 91, and HK G3 are all battle rifles that share the same NATO standard caliber, typically chambered in 7.62x51mm (.308 Winchester), and are known for their reliability and robust design. Surplus 20-round magazines for these rifles can often be found on the market, and they are compatible with all three of these firearms due to their design similarities. Here’s some information about surplus 20-round magazines for these rifles:

1. Compatibility: Surplus 20-round magazines for the CETME C308, HK 91, and HK G3 are typically interchangeable since these rifles share similar design features and chambering. The magazines are designed to hold 20 rounds of 7.62x51mm ammunition.
2. Source: These surplus magazines are often sourced from various military and law enforcement agencies or from surplus stockpiles. They may have been used previously but are usually inspected and refurbished to ensure functionality and reliability.
3. Construction: Surplus magazines for these rifles are typically made of steel for durability and longevity. They are known for their robust construction and ability to withstand harsh conditions.
4. Availability: The availability of surplus magazines can vary depending on market conditions and the specific surplus stock available. They are often available through firearm and surplus accessories retailers or online vendors that specialize in surplus firearms and accessories.
5. Legal Considerations: Always be aware of and comply with local, state, and federal laws and regulations regarding magazine capacity and firearm ownership. Magazine capacity restrictions can vary by location, so it’s essential to understand and adhere to local laws.

These surplus 20-round magazines are popular among shooters and collectors of CETME C308, HK 91, and HK G3 rifles. They provide an authentic and reliable option for those who appreciate the historical significance and reliability of these rifles and prefer to use surplus magazines for their firearms.