I borrowed a friend's DMM and it has big 18 gauge leads (rated for 20A). Using his DMM I got about 2.8A and then using his leads on my meter I was getting about 3A direct driving the LED with a 18650 battery at 4.06V (at rest). So it's all in the leads. I won't have a chance to solder the drop-in back together and do tests on it for a little while, so for now just ignore my current readings because they are not right. I didn't realize it would make that big a difference. Also I kind of wonder if my DMM is calibrated somehow for its tiny leads and if I start using big leads, will I be getting numbers that are wrong in the other direction?
Best bet is to check it against something known, or at least something you can trust more. Low resistance in the meter and leads is not important for voltage measurements where you want the resistance to be as high as possible. For current measurements you want it to be as low as possible. When a meter is measuring current it is in fact measuring voltage over a shunt which is a (hopefully) high precision resistor with a low value, usually around 0.05-0.5 ohms. An external shunt is probably the best way to go and some nice heavy wire to connect the shunt into the circuit.
These leads at DX seem like they are pretty good. I have some on the way now. The writing on the wires in the user picture shows 18AWG which would be 18 gauge wire. That should be plenty.
I also bought some leads on eBay that look just like those, but even though they are listed as 10 amp leads, they have thick looking leads that are all insulation around very thin wires and can't measure the current either (I stripped the insulation and figure they are about 26 gauge wire). I told the seller about this and they agreed to send me 20 amp leads which they confirmed had much thicker copper inside. I got the 10A leads for $1.28 at auction whereas they sell the 20A leads for $6.99 so that was pretty nice of them (but they got me to change my negative review of them). Once I get some of the new leads I will do the tests again and post the results.
It is BRIGHT. When it stops raining I will do a comparison shots with it up against my R5's. Yes has a hole, but I suspect that can be fixed by removing alot of heat sink goop.(its everywhere emitter too high)
I was so pleased with my DX 501B MC-E M bin that I bought three more to get the drop-ins to install in Solarforce or 504B bodies.The current drop-in seems to be just as good or the same as the original batch.I don't hear any whine like others have noticed and they don't seem to get any hotter than my DX R2s or my Solarforce R5s.They do have a small dark donut hole,but it is a small drawback considering the huge light output.I use them on bikes in tandem with a Solarforce R5 or R2 which fills any donut hole nicely.So be patient, DX is shipping them out!
I got my 501B MC-E today. It's really bright, mostly flood. It draws 2.65A on high! There was an annoying donut hole but I just unscrewed the reflector a bit and now it's not visible at all. I can still make out the cross sign but it's very faint and doesn't bother me at all. I'm very picky about beam patterns, as you may know, especially on my R5-A3 and F23, but the MC-E pattern is very nice.