Abstract: A medical pressure indicating injection gun for injecting fluid into a balloon catheter, with a visual indication of the balloon pressure. The injection gun includes a barrel adapted for attachment thereto the body of a syringe, and a bracketed coupling shaft for holding the syringe plunger. The coupling shaft includes pressure gauge marks thereon, and is slideable within a cylinder chamber on the end of a ratchet shaft, and in compression with a spring also in the chamber. A ratchet mechanism is employed for engaging teeth on the ratchet shaft and advancing the ratchet shaft forward, and through the spring the coupling shaft and attached syringe plunger are advanced as well. Pressure build-up in the balloon catheter causes the coupling shaft to retract into the cylinder chamber in compression with the spring and indicate by the gauge marks the balloon pressure.