Last time, I damaged my LED drop-in module because it was rated only for up to two CR123 cells (6V). Two 16340 cells is already 8.4V. Now, I take a closer look at the damaged LED drop-in module and replaced it with a module rated for not just two but three 16340 cells. and that did the trick!
Flashlight Batteries: Replacing CR123s With 16340s
I see if it’s possible to replace CR123 (3.2V) lithium batteries with 16340 lithium-ion batteries (4.2V) on a SureFire G2 Nitrolon with an LED module. Do not try this on a halogen module!