A drug delivery device having a drug container for storing a liquid drug, a first end of the drug container sealed by a plunger, a needle conduit coupled to the drug container, a needle insertion component coupled to the needle conduit, and a drive mechanism coupled to the plunger, the drive mechanism comprising a drive spring (318, 802) and at least one force transfer element, characterized by a drive spring release mechanism comprising a drive mechanism lock, a spring retainer, and a drive mechanism release, wherein the spring retainer has first and second longitudinally extending spring arms (806a, 806b) which are manufactured to be naturally biased inward, and which extend to engage a cam surface of the drive mechanism release, wherein when the drive spring release mechanism is in a locked state, the cam surface forces distal ends of the spring arms (806a, 806b) outward so that portions of the distal ends engage associated stop surfaces (804a, 804b) of the drive mechanism lock, thereby capturing the drive spring therebetween to maintain the drive spring in a compressed state, and when the drive spring release mechanism is in an unlocked state, the spring arms (806a, 806b) release toward each other such that the distal ends of the spring arms clear the stop surfaces (804a, 804b) of the drive mechanism lock; and wherein when the drive spring release mechanism is in an unlocked state, the drive spring release mechanism has been rotated from its position in the locked state, so that the cam surface releases the distal ends of the spring such that the arms flex inward toward each other such that the distal ends of the spring arms (806a, 806b) clear the stop surfaces (804a, 804b) of the drive mechanism lock, thereby releasing the drive spring so that it can expand. a drug container for storing a liquid drug, a first end of the drug container sealed by a plunger, a needle conduit coupled to the drug container, a needle insertion component coupled to the needle conduit, and a drive mechanism coupled to the plunger, the drive mechanism comprising a drive spring (318, 802) and at least one force transfer element, characterized by a drive spring release mechanism comprising a drive mechanism lock, a spring retainer, and a drive mechanism release, wherein the spring retainer has first and second longitudinally extending spring arms (806a, 806b) which are manufactured to be naturally biased inward, and which extend to engage a cam surface of the drive mechanism release, wherein when the drive spring release mechanism is in a locked state, the cam surface forces distal ends of the spring arms (806a, 806b) outward so that portions of the distal ends engage associated stop surfaces (804a, 804b) of the drive mechanism lock, thereby capturing the drive spring therebetween to maintain the drive spring in a compressed state, and when the drive spring release mechanism is in an unlocked state, the spring arms (806a, 806b) release toward each other such that the distal ends of the spring arms clear the stop surfaces (804a, 804b) of the drive mechanism lock; and wherein when the drive spring release mechanism is in an unlocked state, the drive spring release mechanism has been rotated from its position in the locked state, so that the cam surface releases the distal ends of the spring such that the arms flex inward toward each other such that the distal ends of the spring arms (806a, 806b) clear the stop surfaces (804a, 804b) of the drive mechanism lock, thereby releasing the drive spring so that it can expand. a drive mechanism lock, a spring retainer, and a drive mechanism release, wherein the spring retainer has first and second longitudinally extending spring arms (806a, 806b) which are manufactured to be naturally biased inward, and which extend to engage a cam surface of the drive mechanism release, wherein when the drive spring release mechanism is in a locked state, the cam surface forces distal ends of the spring arms (806a, 806b) outward so that portions of the distal ends engage associated stop surfaces (804a, 804b) of the drive mechanism lock, thereby capturing the drive spring therebetween to maintain the drive spring in a compressed state, and when the drive spring release mechanism is in an unlocked state, the spring arms (806a, 806b) release toward each other such that the distal ends of the spring arms clear the stop surfaces (804a, 804b) of the drive mechanism lock; and wherein when the drive spring release mechanism is in an unlocked state, the drive spring release mechanism has been rotated from its position in the locked state, so that the cam surface releases the distal ends of the spring such that the arms flex inward toward each other such that the distal ends of the spring arms (806a, 806b) clear the stop surfaces (804a, 804b) of the drive mechanism lock, thereby releasing the drive spring so that it can expand.