Nice comparisons 
In terms of excellent performance with an MTG2, in a fairly compact format, the MX25L3 is still the best option. The K40M does beat it in output, but the performance gap is very small visually.
I was watching Malcom in the Middle last night, a 90/2000 sitcom.
The troublemaker, not so bright kid Reese said a remarkable thing... "You live in a world of "what if's" I live in a world of "what the hell"" :p
Thanks pinkpanda.
Some weeks ago I modified the X40. Just a basic mod. Stock emitters was too CW for my taste (cooler compared to 1A, and the stock CW emitters in the TK75 as an example) The emitters also had that extra bit of red/pink color in them so I considered them good for de-doming. You can actually notice that in the beamshot if you compare to the TK75. I was not a huge fan of the stock emitters.
Here is a quick peek under the skirt of the X40.
Fairly thick aluminium reflector.
Nicely attached copper mcpcb (probably DTP based on the limited sag, I did not test). I forgot measuring amps at the emitter.
The screws that were holding the driver in place had zero epoxy or anything on them. So in my light it was effortless to get the driver out. (I think Acebeam now makes it much more difficult in all their lights.) R082 and R100 looks like sense resistors. I did not play with them. Light is not regulated when voltage becomes too low, its only got 3 cells, I want to use high capacity cells, and Im not that tempted to resistor mod these lights that got fancy electronics for the charging circuit and such. So I left it stock. Got more pictures if anyone likes to see.
De-domed emitters.
Stock O-ring below the lens was a PITA to get nicely in place on my light since it should have been a bit wider.
For some reason I experienced an issue with sometimes activating strobe when setting the light on highest setting. I tried to make sure that the driver was twisted in a way that made sure the strobe was as far as far way from the magnetic field from the highest output setting as possible, but I still experienced that strobe got activated in some cases. Fixed that with drilling up the driver screw holes with a 0,5mm larger drill bit. That meant I could twist the driver 0,25mm further away. Problem solved! I recommenced to not take out the driver if you don't have plans on trying to modify it. Zero issues with accidental strobe activation in the past weeks.
Numbers:
X40 80190cd (2913 Lumen)
X40 de-domed 151200cd (2625 Lumen)
That is about 90% increase in cd and 10% loss in lumen according to my lux meter. Tint became NW. No red in it anymore, its got a little bit of the typical de-domed tint (with hints of more yellow/green), but not much. It turned out decent. Which is pretty much as good as it gets for de-domed XM-L2s.
I have also measured new (stock) RC40 that I just got in.
RC40 134190cd (3591 Lumen)
All numbers can be compared in the bonus section in OP.
Thanks for sharing.
Did you sometimes experience that your modified X60 went into strobe on highest setting? (I think you said that sometime) If so read my previous post. I got the issue on my X40, but fixed it. Its not directly related to modding the light as far as I can tell.
The only light I experienced that issue with, was the first batch of X60's Vinh modded. I actually haven't used it in months :o
The X60 stock is also gathering dust.
The three lights I ended up using a lot last camping trip were a dedomed X60, dedomed mm15, and a modded TK76. With the TK76 pulling most of the weight.
A modded RC40 was also on the table, in the third mode, acting as basically a lantern. If there is a light to go nuts with, modding, it's the RC40... tons of mass to absorb heat, and built like a tank. Mine, admittedly, now carries a few battle scars.
Thanks for the beautiful beamshots & reviews. According to your pics the K40M is much brighter then the X40 in terms of lumens the X40 is slightly more?
Which light have the most side spill out of RC40 and X60? Im thinking about the outer spill that is close to your feet. Is there much brightness difference between the spill from the lights? (comparing domed emitters vs domed)
Light with battle scars > light with dust :D
If you have too many X60 lights, you can send one my way. I can take care of it. ^^
My first impression of the RC40 is like you say, its built like a tank. But still like a lightweight tank, Fenix style.
:beer:
About K40M vs X40 brightness. The X40 measured slightly higher lumen, but the differences is so small that it could just be that my light meter reads higher on CW lights. These lights have pretty much the same brightness.
When you look at the comparison beamshots and see the K40M as "much brigher", I think that have to do with several things. X40 throw a bit further and put out more light down range. Its not that easy to notice on the wide angle pictures which makes you focus more on the close up/mid range. Second, X40 puts out more light in the mid range wider out compared to K40M. K40M puts more light towards the center, which can be perceived brighter. I would also say that the X40 have a bit more light further out compared to K40M that is not seen on the pictures. Im talking about the very outer dim spill light. K40M spill is pretty much what you see, once it goes dark it goes dark. No gradual transition. X40, have a bit if very dim spill light outside of the "main spill". The transition between zero light and the typical spill light is more gradual. I hope that makes sense. Sorry if my bad descriptions made little sense. That is how I remember them when walking outdoors side by side and also some notes to the pictures. I dont need to explain where K40M is brighter since you can see that.
Here is another mouse over comparison with more zoom. (X40 on mouse over).
I think you will see easier that more of the lumens are hitting the trees in the distance, and that requires more light. You will also see more lights at the edge of the picture on the X40.
Id say these lights have very similar in output, they just have a different beam patterns and emitters.
Yes, thanks for the lengthy explanation!
Very qualitative beamshots and review. Thanks for the effort.
Looking at beamshots online sometimes feels like looking at a murder in a movie.: shrug. Race, that retard light is freaking jaw dropping!!! 
:_( Thank you for the beamshots and lumens numbers 
Cheers guys!
WOW!
That retard light of yours is truly retarded in every sense of the word! 
I wonder if I can replicate that mod. Its doesn’t have to be as insanely bright as yours but I’m setting my sights on my X-100. J)
I really love this forum and I’m glad to be in the right company.
Yeah, its quite retarded, and with good tint. :)
Have not seen your around much lately nightbird95. Hope everything is good.
I just answered your question in this thread regarding your X100.
:beer:
Thanks again RaceR86.
I’ve posted a little lately because I’ve been preoccupied tweaking the mod on the 6X XM-L Bike Light I won from ledoman. I’m also planning to do a tint mix and dedoming on this X6 bike light but it would be after I have solved its driver issues.
That must have taken a hell lot of a time. Thank you for the outstanding beamshots.
Wth is a ‘retard’ flashlight?? I’ve never heard about it but the lumens output is huge!
Well I think ‘retard’ flashlights are flashlights whose mods will only be done or attempted by retarded flashaholics. 
I wish I could be one of them (in a few days maybe? ) because I consider them as the elite modders in the flashaholic world, hehehe… :bigsmile:
Nice beamshots.
i think retarded for lights is the way to go.
@ nightbird95 and DBSAR.. lol.. :p
The light I modified and named the "retard light" was originally sold as an OEM 12 XM-L light. OEM, as in its got no name printed on it. Which means you will most likely see it labeled with various "xxxxfire" as time goes by. Kinfire K1200S is one...
I could have named it Frank, Hank or Lisa.. But I decided on a name that suited the light`s.. ehm.. character better.. Essentially its just 12 emitters in direct drive powered by 6 low resistanse cell for the highest amount of glorious light. :D Nothing fancy (see the thread on it for more details). Its also got a driver in there for modes and such, but the driver is currently retarded, so for now its just full output or nothing. :D I kinda like it that way. J) Output drops instantly by a lot due to voltage sag and heat. Its pretty much as bright as you can make a 12 emitter XM-L2 light (at startup). In the right sphere, with CW emitters and AR lens the light could produce over 17000 lumens at startup, maybe even 18000. Most manufacturers stick to around 3000 lumens in similar sized lights. And those lights are not exactly running cool.. So you can try to picture how this modified light is.. Lets just say it lives up to its name.. ;)
Just by reading the specs, I can see where you are going Not something I have the skills of making ever or anything I would want to touch. Sure sounds dangerous with the amount of cells + direct drive
Verry impressive comparison, would the battery charging handle of the x40 work on the k40m?