As I promised. Pictures are a bit dark because I had poor light.
What is the button you use on the spring? Looks like one from a pair of jeans
Haha. No, this is not component of the pants 
It is silver plated brass. To be precise, it is conductive part of Omten 1288 reverse switch.
BTW. Current bypass is not copper braid for removing tin (as many people use which is only slightly better than ordinary silicone insulated wire but also very short-living). It is a special braid (reinforced with thin nylon threads) intended for mechanical work on powering the speaker coil.
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Question for you, what is additional purpose of using spring bypass for linear driver? I understand for fet direct drive, but not linear drive. Since driver is linear and heating is relate to current not resistance, reduceing resistance in spring will only lead to slightly less heating in spring and slightly more heating in fet where all heat is in causing hot part to become hot faster. Why not leave spring with no bypass to allow additional heat to dissipate away from driver head to rest of flashlight body with more distribution and less work? But maybe my reason is incorrect. Thank you.
The lower resistance here may lead to more heat in FET but only during first 1/3 or half of battery, no? After that it will lead to longer run times with the reduced resistance right?
I don’t like to dispatch heat in place I can’t control. Dispatching heat in places like springs, electric contact surfaces results in damaging and deforming these components in time. You are right that lowering ressistance in flashlight circuit for a linear driver causes more heat dispatch in FET element (but only on fresh charged battery - bigger voltage difference between power supply and LED forwarding voltage for selected current value). But finnaly we have longer time of full current stabilization on selected mode.
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Where did you get the tir throw optic and the nicd looking round thingy;)? do they fit nicely?