You need a way to fine tune it after you solder the lead wires onto it.
I used stranded wire and on purpose I cut it a little long. I did that so I could lower the resistance, after soldering the test leads, by letting solder wick into the wire between the 2 connections little by little. If it is lowered too much, then I could squeeze a notch in the wicked portion with my diagonal cutters, introducing a small restriction at that point and thereby slightly increasing the resistance. It wasn’t easy.
I used 14 gauge stranded wire, however it would have been easier had I used 12 gauge or better still, 10 gauge. Heavier gauge wire means that you would be working with longer pieces and would have greater “resolution” to work with. Solid wire could work too.
Measuring high current levels in our flashlights is not easy in and of itself, but when you introduce the resistance of the .01 ohm shunt resistor in most DMM’s AND the resistance of the test leads AND the resistance of the contact points, the reading that you get will NOT be what is actually being delivered to the light in real life.
Modded SRK type flashlights with multiple emitters could use 20A or more. My modded 6 - XM-L2 is pulling in excess of 16A.
I am working on integrating a shunt resistor to a replacement tail cap contact board complete with braided springs so that I can install it onto the back of the light. Only then, when exact operating conditions are met will I be able to get a true measure of the amps drawn.
I first calibrated a shunt resistor in this post, It was difficult but not as difficult as the .001 ohm one.
Remember, I did it, and you can do it too.