I make these custom drop ins for myself and sell a couple every once and a while. They can run on 2.8-6.0 volts so 2 CR123s would work perfect. I pot them with Fujik and have them mounted on rifles, shotguns, pistols you name it they handle recoil fine. If you have your heart set on 2 CR123 batteries this is probably your best bet. I have that ramping drop in from DX I converted mine to an R5 for an extra 100 lumens very cool drop in. Send me a PM if you want more info on my drop ins.