^^^^This. I replaced all the heads on my 6Ps with Malkoff heads and they are top notch. Register your email with them and they will send you a first time buyer coupon.
I am upgrading both my M9 Laser Technolgies direct mounts, (like you see in the bottom middle), the later after they became Surefire TG Mount versions like you see in one of the top row guns,
hand held combat lights,
Like this era-
And G2, nitrolon line lights I start getting back around 2006.
Like these
These nitrolon are like $50 lights. Not sure if I want to spend forty plus bucks each replacing the lamp in ten or so of them.
It basically seems despite what they are advertised for, nitecore and some of these lithium rechargeable batteries are just too strong for the older incandescent.
Running a full powered LED module in a completely Nitrolon bodied light doesn’t allow anywhere for the heat generated to go. It’s recommended to use an M61L (or LL if it generates enough output for the task). If it’s got an aluminum head, then the full powered M61 can be used, since the head will transfer the heat to the air.
The problem with your incan lamps is that two Li-Ion cells in series are delivering 8.4 volts (without considering sag) to a lamp that’s designed to operate from 6.4 volts (without sag). You can run one Li-Ion with them, but then you’re under driving the filament, which while not catastrophic to it, isn’t ideal. If you want to run two Li-Ion cells with an incan lamp, you should use a P90 or P91 lamp.