Explosive cutter assemblies and methods include a liner having a single unitary body, and an explosive charge disposed within the liner. The explosive charge includes a continuous unitary body of explosive material having a first area disposed in association with an inner surface of the liner and a second area extending from the center of the assembly to the first area. A detonator can be used to ignite the second area of explosive material, causing propagation of a detonation to the first area, which in turn causes deformation of the liner and projection of the liner toward a target to form a cut. An adaptor sub having a detonator within can be inserted into the cutter assembly to secure the assembly together, position the detonator in association with the explosive material, and engage a conduit usable to raise and lower the cutter assembly and transmit a detonation signal.