Intradermal delivery of vaccines with jet injection is one of the alternatives to conventional delivery techniques with hypodermic needles via the Mantoux technique and multi-puncture devices etc. However, for a given fluid, the effects of various parameters related to injector design, as well as skin properties are still not well understood. While the key design parameters are orifice diameter, jet speed, cartridge volume, and standoff distance, we must also consider the applied load of the device on the skin and axial skin tension. These parameters are all studied herein using different ex vivo models (guinea pig, pig, and human skin) and different fluid viscosities. We find that the applied load can have a significant effect on the amount of drug delivered through the skin, as well as the fluid dispersion pattern in the intradermal tissues. Regardless of skin type or fluid viscosity, we show that minimal standoff and applied force loads of approximately 1 kg (9.81 N) should be used to maximize injection efficiency when targeting intradermal tissue with the spring-powered device used in this study.