RTG Parts LLC - Here's one you don't see very often. The HK11 is essentially an HK91 automatic rifle fitted with a heavier barrel for the light support machine gun role, borrowing
HK 21 and 23 - Modern Firearms
They should change automatic rifleman on MEA to have the HK-21 instead of the drum mag G3 : r/joinsquad
Beltfed Precision Products HK 23E Barrel Assembly-5.56-17.7"