Probably testing surveillance systems. That's the go-to place for doing so, I presume because of an established 'test range'.
Testing surveillance systems in an established range? Can you elaborate? Both N350JW and N213LA are apparently registered to Falcon Air Service Inc. However, I've read that the FBI has been using C208s/B350s under front company's for surveillance purposes.
If surveillance is the case it's scary because they're in the sky 5 days a week. I'm just trying to figure out the who what and why these planes keep flying over Hagerstown on a daily basis.