Part of the problem is that a man can carry a lot of ammo, sure a load of 180 rounds in 30 round magazines is common but so is more.
In the Vietnam war US soldiers often carried 1000+ rounds and more ammo for machine guns, a few hand grenades.
Why did they carry all that ammo? because when your ammo runs out you are no longer in combat, you are dead.
If you have a fixed position then it will have its own ammo stored there.
If your expecting a fight you'll carry more ammo, so raiders will probably come with a lot of ammo for sieges.
In the Vietnam war US soldiers often carried 1000+ rounds and more ammo for machine guns, a few hand grenades.
Why did they carry all that ammo? because when your ammo runs out you are no longer in combat, you are dead.
If you have a fixed position then it will have its own ammo stored there.
If your expecting a fight you'll carry more ammo, so raiders will probably come with a lot of ammo for sieges.