Abstract: An apparatus for mounting a tip cap having a maximum diameter over a syringe subassembly having a syringe body with an end carrying a needle has a holder holding the subassembly with the needle substantially on an axis and a tubular guide having a feed passage generally centered on the axis adjacent the holder, of an inside diameter greater than the maximum tip-cap diameter, and open toward the holder. A stop can move between a blocking position between the guide and the holder and an unblocking position offset therefrom. The tip cap is fed through the passage to a position arrested on the stop in the blocking position thereof. A nozzle opening into the passage injects pressurized gas into the passage and thereby spins the tip cap in the passage about the axis. The stop can then be moved from the blocking into the unblocking position for displacing the spinning tip cap from the guide onto the syringe subassembly in the holder. The nozzle opens tangentially into the passage.