Using two AA's will require a boost driven P60 type drop in. Most drop ins use buck type converters, though some appear to be buck/boost, though not the Sure P60 LED's, or the Malkoff M series.
The extender added to a two cell Surefire body will not affect output using LED's driven by constant current LE's, though could, if resistance was high, affect runtime. Mostly considered a non issue resistance wise.
Bill
Thanks for clearing up the resistance issue Bill.
I recently received an M30. Excellent device.
I am running it in a Surefire 6P with a 1 cell extender.
I am using 2 AA alkalines as my first test batteries.
I have no fancy equipment to measure outputs etc.
I used 2 AA batteries that come from a 4 cell pack that cost $1. El cheapo and crappo.
Using these cells, the M30 matched my Wolfeyes HO 170 lumen rated CREE lamp(2 x AW 17500's).
I noticed no drop in output for 1 hour and 5 mins, At which the lamp did not shut down, but continued to give useable light......I discontinued my highly scientific tests at the 1 hour 30mins mark.........As after the first drop in output that I noticed, well this is when I will be normally changing to fresh cells. Good to know it wont die on me flat out though.
During the whole test the light only got warm......never was it uncomfortable to touch or hold onto.
I'm Impressed....I'm getting a really bright light that runs for 1 hour or there abouts off 2 AA alkalines.
I tried an AW lithium-ion and it was very bright.