There is a lot of factors, battery, battery tubes, springs and so on, also how angry a person you are will affect your DMM reading as the harder you press down the higher the reading you will get, some under read some over read some are better then others, some cost more then others but most of this means shit once the tail cap and switch is screwed on as the current will be lower again and even lower at the led then what people get with 1 inch thick DMM leads at the back.
I'm crazy i use stock leads cheap DMM, my fluke went walk about when we moved, i have brought another cheap one to keep my old faithful in check it should be here soon, but you will get different measurements from different spots on the thread and battery tube and different readings depending on how warm or cold the battery is and since there is resistance in the switch, tail cap, threads, threads with grease, battery, battery tube, springs, solder, driver, pill, led wires and so on what you get at the tail with your newly modded DMM leads is not what the led is getting any way.
I have seen some crazy thine wires on some lights, my KD C8 that people claim 3 + amps, mine had wires from the driver to the led thiner then a bit of my hair and i have thine hair, i find it hard to believe that what people got on there tail cap readings is what the led got a skinny bit of wire poorly soldered like that would struggle at 3.6 volt at 3 amps IMO.
So maybe stock DMM leads reads closer to what the led is getting, but then again some of my lights seam to pack more of a punch then my cheap DMM says with standard leads shows, maybe Ive never seen a xm-l driven at 3 amps, but i know i have. but my eyes can not tell the difference between a xml driven at 2 to 2.5 amps and i can not tell the difference between 2.5 and 3 amps, this is another story about tint and what people see, but any how.
Some times i feel its more of a pissing contest, my car has 600 BHP and does 4 mpg and yours is 200 BHP and does 35 mpg and because we are not using a sanitized system e.g same meter, same thickness same length leads and are not all pressing the same hardness and using different batteries and people do tail cap readings with less then 4.2 volt we will always get different readings and then on regulated lights it does not really matter any way.
But in saying all this a claimed 3 amp light from forum members will sell more lights then some one claiming 1.5 amps, i rather under estimate mine then over estimate mine, so did this post help with the confusion or did it just show Ive had a ruff night and add more lolls.