After the Browning BAR was adopted, the military did what the military does and came up with a doctrine for it, support gear for it and all kinds of related jobs. A lot of people think of it as a one man show. Not like the tripod mounted belt fed machine guns with a crew to serve it. But it was. And there was some interesting support gear for the BAR crew.
Above is a belt to be used by the BAR gunner. The black portion is a “cup” for sticking the butt stock in to hold during walking fire. To it’s right is a double mag pouch for the M1911 as the gunner was issued a pistol as well. Later BAR belts only had 6 large pockets.
Other than the BAR gunner himself, there was the 1st assistant. The assistant, wore a special belt that was a combination of the BAR belt and the cartridge belt for the m1903 rifle. You can see the four pouches that held 2 stripper clips of 5 rounds each. Around the belt behind those you can see the larger pockets that held two BAR magazines each.
In addition to his belt, he wore two bandoleers across the chest, with three pockets each for six mags.
Below is the belt the 2nd assistant would be wearing. Four pouches for a total 8 magazines for the BAR and his forty rounds of .30 caliber ammunition for his M1903. The 2nd assistant may or may not have had the bandoleers.