How big is the facility? When I worked for General Dynamics the site I was at had 30,000 employees and the main building was a mile long. It wouldn't be a stretch to justify 5 auditors for 5 days there. If it's a 5-person machine shop, I'd say it's extreme overkill.
In my experience it is very common for military agencies to perform quality system audits with many more auditors and for a longer time, compared to certification body audits.
Because of the additional audit-days, such audits tend to scrutinize the system in much more depth than CB's. On the other hand, sometimes, the qualification and competence of the auditors is limited, leading to questionable findings along the way.