0 (prereq). Have MX SW with 100 round 6.5mm magazines, and an MX 3GL with at least a 30 round 6.5mm magazine and at least a 3GL tube grenade (idk if the 3GL nade is truly needed)

1. Look at MX 3GL (loaded, idk if it matters) on ground and open inventory
2. Drop MX SW (loaded, idk if it matters) with right click (idk if drag and drop works too)
3. Pick up MX 3GL with right click (idk if drag and drop works too)
4. Sometimes, the 6.5mm 30 round magazines load themselves into the Grenade Launcher attachment by themselves, and are able to be shot independently from the main magazine. However, when the 30 round magazine is depleted, it cannot be reloaded (normal 40mm grenades can be loaded)