Alright, I'm not exactly new to Surefire lights, but I'm relatively new to the Scout series.  As of right now, I seem to be having a slight issue that I just noticed with an M600U mounted on an IWC Dropwing mount.

So, the light is currently mounted on a KAC RAS via the IWC mount.  I was dry firing and noticed that the light was momentarily activating for a split second without me touching the tailcap.

Every time I would rack the CH and let the BCG ram home, the light would discharge for a split second.  Also, if I dry fired the rifle, when the hammer would slam home on the firing pin, the light would activate for a split second.  Just seems odd to me.

I have another M600U that is still on the stock picatinny mount that doesn't seem to exhibit these symptoms and I've had a handful of different Millenium series lights that didn't either, so it has me wondering.  I'm not all that comfortable having a weaponlight that discharges without my input and it seems this may be an issue considering I have another one that doesn't do it.

Has anybody else seen this?

Odd, to say the least.  Make sure everything is installed correctly tighten head and tailcaps.  If it still persists try changing the batteries.

I've seen and experienced the same issue when I had the same setup. I've also experienced it with the stock mount, though I don't recall it being as bad as when using the IWC mount. I just attributed it to battery bounce in the light and moved on with it. It never bothered me and the millisecond of light that flashes was a non-issue when I noticed it at night. I figure if I'm racking a round in the dark and they're close enough to see a millisecond of light, then me chambering a round would give me away first.

Thanks for the input.  I'll give a battery change a shot, but you're probably right that it really won't matter.

My guess it its only happening when the chamber is empty.

During live fire, my bet is it doesn't happen.

I've had it happen on a SF light, but I cannot remember which one...could have even been an old G2 when I rigged those up as weapon lights.

Sometimes, batteries can be the cause, try that.....otherwise, test it under live fire, or have surefire replace the tailcap.  Reality is that it should NOT be happening.