Follow the same strategy as for Quick Load; all the factors mentioned there will help with this one too.
If trying to get this achievement artificially (i.e. firing a single shot, reloading and so on) take the Rail Rifle, as it won't affect your ammo supply as badly as any other weapon.
If you switch weapons before a fast reload is completed, ammo will not be loaded; though the game still considers that as a successfully completed fast reload. This allows you to get this achievement with minimal ammo loss.