I was gonna say that probably wouldn't help but then I saw the modern weapons. They would rip through the opposition like they were field mice under a roto tiller. Just bring like....all the ammo. You're gonna need to HOLD Harper's Ferry for the long term and that is gonna be tough with only 4 automatic weapons. With the proper displacement of forces with at the time current weapons i think it could be done, mostly cause a key access point is a bridge which would be easy to guard with an automatic weapon against flintlock guys. How to deal with artillery once it gets to that point would be a huge issue.