Gladius tailcap feel when changing batteries

I bought my Gladius not so long ago from this very site. Since then it's barely left my side - my Surefire L2 has been relegated fo glove-box light.

I've been toying with it with one hand while doing other things, getting familiar with it, and I'm fairly sure I've come across something that's not quite right, but I wanted to ask here, just in case.

When replacing the tailcap after removing it, the first couple of turns feel slightly grainy. Gradually, the tailcap tightens up, and when it's covering the rubber O-ring, it feels like there's a very definate metal-on-metal resistance that makes me wonder whether it should be that tight. I know it has to be tight with the O-ring to seal it, but this feels like metal on metal, and I'm not quite convinced.

Is this the experience everyone else has? If not, do I need to grease it? If so, are there recommendations for the correct type of grease, and where to buy it?

In mine, nothing feels 'grainy', or like metal-metal-resitance. Thread runs smooth until the O-ring's covered, in which case it bottoms out. No screech, no nothing, it just stops.

Appears to me that you should clean and lube the thread.

Get NyoGel 760G from lighthound.com.

When I encounter a threaded assembly which is not smooth enough I try cleaning the threads (both sets!) with an old toothbrush to remove any machining debris from the threads. Once grease is reapplied (if there ever was any) most have been very good afterwards. Those Gladius threads seem like a finer pitch than other lights, so any unwanted gunk or embedded chips probably makes them drag more than other lights. HTH.

Paladin