The fact of the matter is many Jugs had 6 guns. This wasn't always up to the pilot. You flew what you had, you had to stay in formation, you probably all flew the same configuration. Even the early jugs often only had 6 guns adn 267 rpg. The standard loadout for 8 guns was often only 200 rpg. Some 6-gun setups went as high as 300 or in 1-2 cases I've seen 310 rpg on a 6-gun setup, but for the most part 267 was it.
The large ammo load was never used. I wish they're take it from the game. 425 rpg? Poppycock. 300 seems about the most (even that's the exception to the rule) and that only on the 6-gun setup.
Hitorically speaking 6 guns/267 rpg is the only accurate loadout currently on the jug.
P.S. In the PTO there was more than ever a desire to lessen weight. Early on they had no range, and every pound was that much less they could fly. Later when they had the range, they were over-burdened with late model Ds and then N models as well. They would load up 3 bombs, rockets, or rockets and DTs, or any combination. To counteract this heavily overloaded plane on rough unfinished landing strips as well as short runway and trees at the end, it was not uncommon to remove all but 2 guns and have a reduced ammo loadout for them. Even still, some of these ground pounders became aces.
You didn't need much to shoot down the Japanese craft. A hard fart and they'd keel over justabout. 8 guns was overkill and if the option was to remove 2 guns and half the ammo, and be able to fly 100 mi further and still down 10 enemies, it was worth it (vs having to turn back from lack of fuel)