A medicine injector in which a barrel with a receiving cavity is adapted to slidably receive a syringe subassembly for axial movement therein. Upon removal of a safety and release of a syringe driver, the syringe driver moves forward and injects the syringe needle. Penetration controls are shown for controlling needle penetration depth. In one form the penetration control uses a sleeve and spring which are radially adjacent. A cushioning ring or other cushion may be used to reduce syringe breakage. A load distribution and guide ring may be used to distribute loading applied to the syringe and help guide the moving syringe.