A method involving a syringe, a pre-filled cartridge, a needle, a guard, and a release mechanism is described. The method may involve inserting the cartridge into the syringe. In some versions, the method may involve releasing the guard to cover a portion of the needle. In some versions, the method may involve the release retaining the guard in a retracted position. In some versions, the release may be operable to be actuated to release the guard. In some versions, the guard may be extended and locked once extended to cover the needle.
