When using the M-60 links, the H&K 21 has a higher probability to have a failure. The M-60 link requires no modifications; however, it requires full-power ammunition because it has significant drag through the belt-fed mechanism because of the thickness of the links creating a higher probability of jamming or failure to eject the link.

Belts made for the Mg3 in 308 must be reconfigured by reversing through feed in and adding a starter tab. The starter tab is a must for ease of feeding through the H&K 21 fed mechanism. These come in 50-round belts and can be put together to make a 100-round belt.

The Mg3 belts have proven to give the best performance with very few jams. The Mg3 belts being slimmer create low drag through the belt-fed units. The belts should always be loaded with a starter tab and first round empty in the belt and the last link should be cut to about 1/3 of original size. This will further reduce the tendency for the gun to crush the last link. We recommend always firing your 21 using the 50-round drum or the 100-round belt box as this greatly reduces the effect of weight of the fully-loaded belt weight over 5 lbs. pulling away from the belt feed during the firing and greatly reducing jams. TSC has pre-made belts available made from the Mg3 belts in 50 rounds for our drums and 100 rounds for the belt box.