It's easy to imagine that not every Survivor community will be fortunate enough to have a Cold-War weapons depot, or a DARPA experimental lab with weapons such as Semi-Autonomous Robots in cold storage nearby. What are some powerful Old Tech options ? Alternate Ideas for the State of Decay Class Four World - in terms of weapons are - Ballistae ! In a scenario where wood and scrap steel are plentiful, but explosives, shells and rounds are in short supply - a community might be compelled to invest much more heavily in the development of effective long bows, compound bows, crossbows and emplacement bows such as Ballista or Ballistae. https://en.wikipedia.org/wiki/Ballista One such variant based on an image from Trajan's Column was recently reconstructed with guidance from written descriptions and comparisons with archeological finds. The Roman re-enactment group Comitatus commissioned the build and received a powerful field weapon. http://www.comitatus.net/armyballista.html A Weapon such as this could be very effective in defense of Survivor Communities and Outposts. Devising such weapons would require library research, wood working and metal craft - and testing. Once constructed - the above version could pin a Feral to a tree. I imagine this ballista could also take down Juggernauts - if one were to nail 'em in the head or spine. Survivors based in the present day could seek to improve on this Roman-based example if they desired increases in power, range, payload, efficiency ( meaning it requires a smaller crew to load and operate ), and a quicker reloading and firing time.