Finally, I have completed my first ever light. When I first joined CPF I had never thought that I would be machining my own light, it was only after seeing that Don guy's stuff was I inspired make chips.
The light uses a Cree XR-E driven by a BB400 running on a CR2, it gives off an even circle of flood. What you see that looks like a reflector is only for cosmetic purposes only, it is threaded and its main function is to maintain pressure between the 17mm UCL, o-ring & bezel lip and to keep the emitter dome from touching the UCL.
It is quite a small light as you can see in the comparison pic below (uses 6061 so the walls aren't as thin as it can be if I had used 7075). It uses the battery pack with an attachment point, the flat bottom pack was made first but was too short (not enough thread engagement) and the o-ring groove cut too deep (loose when turning, not water resistant). Problems when going "free style"....
The bottom of the battery pack has a raised nipple for negative contact, but that also means there is battery rattle when the light is in the "off" position. Time to go find some foam pads.