Surefire G2 draining batteries

I have a Surefire G2 Nitrolon that will drain its batteries over the course of a few months (with little or no use). Due to its brightness, red filter and ergonomics, I like this flashlight as my "tactical" (I hate that word) flashlight, keeping it locked up next to a HD firearm.
I do feel I can't depend on it though, as if it has been sitting with batteries in it for a few months, odds are they will be dead.
Is this a normal problem for Surefires, or this model in particular? The only other "real" flashlights I own are a couple of Fenix lights which run on the same batteries (CR123s), and do not seem to have this problem.

Any suggestions on how to remedy this other than leaving the tailcap off - which does stop the batteries from draining, but defeats the purpose of having this be my go-to light for things that go bump in the night.

Heard about older G2s without the lockout tail cap. Think they made a change like 4 years ago to make them have lockout (where's Size15s?). You could have a older version? Or maybe a bad switch in general. Not sure myself, but remembered seeing the lockout tail cap as a new feature for the G2 at some point.

1. What brand of batteries? Good quality 123's last a long time in storage. I have a pair of Duracell's that came with a Surefire 6C (the first lithium powered light) and they can still light a P60 lamp module. I think these cells must be at least 20 years old.

2. An incan. light shouldn't drain cells if there's no electrical connection. If there was some sort of parasitic electrical drain, it should be visible at the lamp filament.

Has done it with both Surefire and Paragon batteries - multiple sets.
In fact, I just pulled it out last night and the batteries, which were new about 6 months ago and used very little since then, were dead.

If there was some sort of parasitic electrical drain, it should be visible at the lamp filament

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the lamp doesn't appear to have any current going through it; at least not enough to glow at all. I can't think of how there would be another path for current to flow through, but there must be.

Any thoughts as to how I could check around with a multimeter to find where the electricity is going, or modify the tailcap to allow it to work if pressed but make sure there is no contact otherwise?

Does the internals of your tailcap fall out when you open the back?
Older G3's did so they lacked proper lockout.

But this will be seen, any contact and the light will turn on momentarily unless its a high resistance contact being made.

Nothing falls out of the tailcap, but when removing and replacing the tailcap, the light goes off and on.
It starts doing this right when the threads engage and will do it a few times while screwing the tailcap all the way on.
You can also get it to come on by wiggling the cap when it's only partially screwed on.

I emailed Surefire yesterday to see if it would be covered under warranty, but have not heard back as of yet.

eastsiderich said:

Nothing falls out of the tailcap, but when removing and replacing the tailcap, the light goes off and on.
It starts doing this right when the threads engage and will do it a few times while screwing the tailcap all the way on.
You can also get it to come on by wiggling the cap when it's only partially screwed on.

I emailed Surefire yesterday to see if it would be covered under warranty, but have not heard back as of yet.

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I bet it's the tailcap. For SF, it's easier and faster to call them. They'll probably send out a whole light.

That'd be sweet!
I'll have to let y'all know if/how they resolve the situation.
Maybe I'll try the phone tomorrow.