An occlusive medical device system may include an elongate shaft having a lumen extending longitudinally through a tubular body portion and a plurality of retaining arms extending distally from the tubular body portion. An occlusive medical device may include a proximal tubular mounting portion fixed to an expandable occlusive element. A release wire may be axially translatable between a distal engagement position and a proximal released position, the release wire having a distal engagement portion and a distal retention portion distal of the distal engagement portion. The distal engagement portion may be configured to engage the plurality of retaining arms in the distal engagement position, thereby urging the plurality of retaining arms into releasable engagement with the proximal tubular mounting portion, wherein when the release wire is in the proximal released position, the plurality of retaining arms is deflectable radially inward to disengage from the proximal tubular mounting portion.