Is it safe to use a quality 16650 in the Streamlight TLR RM2? No word back from Streamlight about this yet.
Thx!

I can't tell you if this particular combination is safe. Maybe.

 A couple CR123A in series would be around 6 - 6.5 volts. However, the light will regulate that down I'm betting. A single 18650 has a nominal voltage of 3.7

Bottom line is, it's not likely to hurt it to try I wouldn't think. However, somebody who knows a lot more about the electronics of weapons lights could tell you better than I can. There's other possible considerations.

I have used 16650 in my RM2 and a surefire without issues. I dont think it gets as bright as with CR123 but it works.

For what its worth, I use 16650's in my SF G2X's and 6PX's.  They don't get as bright, but for a handheld light for me, its not a deal breaker.  I wouldn't use them for the cost of CR123's otherwise.

There's an odd deal, where it doesn't read the double press on the low/high if you go too fast.

OP... get a couple of SureFire rechargeable 123s and you accomplish what you want.

Actually, I already have those.
However, two of them still have less than half the capacity of 16650s, hence my interest in 16650s.
But thx for the suggestion!

I just heard back from Streamlight, and they don't recommend rechargeable batteries in any of their products not designed for them.
I understand how a couple of RCR123'[email protected] could cause overvoltage problems, but a 16650 would be 3.7v and thus under voltage so that *shouldn't* cause problems, iirc.
I don't know if this is due to actual technical issues or is just a 'cya' in case someone's Streamlight gets damaged from using over/under-voltaged rechargeables.