Can’t remove bulb — British Army Right-Angle Torch (Linpac, possible Fulton MX991/U clone)

I picked up this flashlight at a local military auction for next to nothing, and I was surprised to find that it still works. The original incandescent bulb is pretty weak, though, so I’d like to replace it with an LED.

Before I can do that, I need to remove the bulb and that’s where I’m stuck.

I’ve tried unscrewing it, pulling it straight out, rotating it, etc., but it won’t budge. It almost seems like there’s a metal "skirt" or collar holding the bulb in place. At this point I can’t tell whether it’s seized or if I’m just missing the correct removal method.

Has anyone worked on these Linpac/MX991-U style lights before? Any tips on how to get the bulb out without damaging anything?

Last image is the reference of the exact same model I've got.