Half load
Using the half load method enables you to prepare the weapon for firing without opening the top cover. The original 250 round browning belts, and the M1 link system, had a brass (steel on the links) starter tab which you poked thru the feedway from left to right and pulled it tight pulling cartridges over the belt holding pawl. The first round would bump up against the left side of the extractor, the first pull and release of the bolt handle places a cartridge under the extractor( the half load) the next pull and release places a cartridge in the chamber and advances another cartridge under the extractor (full load) and awaaay you go.
Usually I open the top cover, because I mostly use 100 round belts which have only a brass grommet instead of the tab.