Abstract: A remote injection device for animals comprises a barrel with a piston slideable within the barrel from an initial retracted position at one end of the barrel forwardly toward the opposed end of the barrel to discharge liquid in an injection action through a needle at the forward end of the barrel. The piston is held in a retracted position by an O-ring on a release member which projects through an O-ring carried on the inside surface of the barrel. The inner diameter of the O-ring on the barrel can be adjusted by axial movement of the pair collars on the inside of the barrel. This adjusts the amount of force necessary to push the release member O-ring through the outer O-ring to release the piston to be moved by spring to the discharge position. The barrel can be mounted either upon an arrow type projectile so the impact forces are sufficient to release the piston upon engaging the animal.