Add 1 Surefire
A19 one-cell extension to your M2 and you can fit 2AA's. Add to that, another
A14 Surefire extender and you can fit 3AA's. The
Spiderfire extension tube is the same size at the A19. I don't think that there is a Solarforce tube the same size as an A14. The Solarforce e18 is not equivalent to the Surefire A14. The A14 is a Surefire proprietary sized tube that is about the 3/4 the length of the e18. The A14 was originally designed to convert the Surefire 6P to use B65 rechargeable battery.
You will need an LED dropin with an input voltage of 3.7 or 3.8 to 6/9 volts to get maximum use out of the AA's. There are many LED dropins available. The standard Surefire P60 incandescent bulb will light up but it will be pretty dim.
This will work in your M2 but...I would not recommend it in your stock M2. You will lose the ability to utilize the combat grip and the M2's shock absorbing head is not ideal for use with LED dropin bulbs. The shock aborbing head may cause the LED to run a higher temp than designed or overheat after extended runtimes. Also the AA batteries will rattle in the tube.
Nevertheless, it is good to know that these combos can be used to run AA's. I keep an old Surefire 6P with an old A19 extension with one of my older Q2 LED dropins at work knowing I can use two AA's to power the light in the event I am out of CR123's.
For the price of the extension(s) you may be able to buy a Solarforce 2AA body for the same or less.
