You can call Jim for delivery of a weapon at the clubhouse. There are special weapons available after completing specific missions.

Unlockable	How to Unlock
Automatic Pistol	Finish the "Bad Cop Drop" mission .
Micro sub machine gun	Complete the "Clean And Serene" mission.
Pipe Bombs	Finish the "Hit The Pipe" mission.
Sawed-off shotgun	Complete the "Clean And Serene" mission.