The CETME model C isn't really a clone of the HKG3. They were developed simultaneously and parted just before the designs were finalized. Unfortunately, they parted far enough back that only a few parts interchange, such as the P-grip and magazine. There may be a few others, but the list is short.
The Century CETME, built on the cast stainless steel receiver is probably the better of the newly made versions.
The best HK-91 clones were recently made by Interport and available through AA-OK. They used a HK licensed receiver, made by FMP of Portugal and assembled by Special Weapons.
The latter Special Weapons SW-3's are essentially the same as the Interports, using the same FMP receiver, but the earlier SW-3's used the same cast stainless receiver that, with modifications, is now being used on the CETME clones.
SW has been advertising a complete HK-91 clone kit, sans firing pin so as not to be a complete gun, for $500. These are supposed to be new or near new parts. You'd have to have someone like RDTS or Machine Gun Kelly's put it together for you.
