Gun Block Alum Kit, #02 Chamber/PCTPolyurethane Machinery Corporation (PMC) PMC is pleased to announce the new AP 2 Gun Block Kits. Spray Guns sometimes require a complete gun block kit that can quickly and easily replace the head on an existing gun. The sprayer may want to change the entire gun block when it is ready for maintenance or would like to change the chamber size for a different output. The change is quick and easy and the kit is complete, ready to be installed onto the gun.