Help needed with a Malkoff / Surefire Lego (long-ish post)

Hello, CPFers! I'm trying to put together my first Lego, and I could use your help (please note that I've bolded some things in the hopes of increasing readability; I hope it's not perceived as obnoxious).

Here's the Lego build:

• Malkoff MD2 head
• Malkoff MD1 body (modded by another CPFer; see the CPF Marketplace)
• Surefire Z41 tailcap with Oveready ZeroRez Shorty Z41 upgrade and 15mm spacer (if I understand correctly, this should turn the tailcap into a watertight, tailstand-capable twisty, capable of using up to 50mm cells if the spacer is removed)
• Possibly a Delrin tail shroud, if a pocket clip is desired
• (M60F or M31L or M31LL) with high/low ring
  • M60F advantages: I perceive it as being tougher, due to the acrylic encapsulating the LED; can be used with a 16340 (or 18500 if the spacer is removed)
  • M31L and M31LL advantages: regulated at 3V; can be used with a AA if the spacer is removed; better runtimes expected compared to M60F

Questions:

1. Are there any physical incompatibilities you can see with this build? In other words, have I chosen pieces that will actually Lego together correctly? I believe I have, but as I said before, this is my first Lego build.
2. How's the output of the M60F on a single CR123 primary? I realize it will be in direct drive at this voltage, but does anyone have ballpark lumen figures for the M60F at 3V on both high and low, or approximate runtimes on a single primary?
3. Does anyone know how the M31L or M31LL with the high/low ring will run? I'm particularly interested in how useful the light is on low, and what runtimes I might expect on a single primary.
4. For a primarily floody beam, should I consider putting a frosted lens if I end up using the M31L or M31LL?
5. Do you see any obvious improvements I can make? My motivation and desired properties are below.

For those of you who are curious, here are the desired properties of the light, based on my motivation to come up with a Lego for an ultra-reliable backup light - I may EDC it for a while, or eventually throw it in a glove compartment and forget about it for a few years. But I want it to be a light that I know will work (I do realize nothing is fail-safe, but I'd like this to be as reliable as reasonably possible).

• Twisty switch
• Runs off a single primary
• At least two outputs
• Long run time on low
• Reasonably bright output on high
• Potted electronics
• Can tailstand
• Primarily floody beam
• Submersible and durable host (reasonable submersion - does not need to be a dive light)

Any and all feedback, links to other threads, beamshots, measurements, etc. are welcome. Thanks for any help!

If you plan on using a single primary, MD2 head with hi-lo ring + MD1 body + SF Z41 with Oveready ZeroRez Shorty Z41 and M31x is a very good choice. If you want to run with a single RCR123, swap the drop in with M61x.
You can use a diffuser to get a flood beam, or buy a M30F or M60F drop in.

There's no real advantage to the M60 in terms of "toughness" in my opinion. If the M31 is tightened down in the head as it should be with a lens and gasket, it'll be at least as waterproof as the M60 and the electronics are potted in the M31 as well so you're protected against shock and dust, water, etc on the battery side. Plus, you get a significant increase in efficiency with the updated LED in the M31.

That said, I don't think you're gaining that much in terms of reliability with the twisty switch either. The Malkoff tail caps come with McClicky switches which are great, and since the Oveready cap was designed for Surefire lights and not Malkoffs, I would be mildly concerned that slight differences in the threads would cause wear after working the switch over and over in twisty fashion over an extended period. Also, remember that twisties become more prone to water ingress when they're being operated because the o ring is no longer static. With a clicky, the tube o ring stays static and the switch boot stays clamped and doesn't move relative to the cap.

I might instead have whoever is modifying your MD2 just cut the body for a 50mm cell instead of 34mm so you can still run either a primary or a AA as you had planned and go with the Malkoff tail cap so everything matches.

That said, your proposed combination would work as well and would very likely be quite robust.

Good luck and let us know what you wound up with.


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Thanks for your replies.

Redhat: Thanks for confirming that the Lego has sensible pieces that will actually fit together. A diffuser is a good idea, especially since I don't think the M30F is in production anymore (but maybe I can snag one in the MP, if I'm lucky).

GeoBruin: Thanks for the explanation regarding the durability of the M60 and M31. I had a suspicion that I was just being silly, so it's nice to get confirmation! The McClicky is indeed a nice switch, but I did have a McClicky failure a couple months ago in one of my MD2 tailcaps. This is what led to my wanting a (hopefully) more robust twisty on at least one light. Your point about water ingress due to o-ring movement is well taken, and something I hadn't considered. I think that, for my purposes, the twisty may still be a better choice overall, as I expect the light to rarely get wet anyway. Thanks, also, for your reassuring comments about the build itself.

If anyone has used the M31 series with high/low ring and would like to chime in about the output levels, please feel free! I think I've decided to go with the M31 series, but the number of "L"s depends on the low outputs and runtimes. Any information is appreciated (I had a hard time finding anything when I searched).

I have an M31w in an "MD1" with a high/low ring and the low is quite low on a primary. Not moonlight low, but maybe 7 lumens plus or minus a couple. With previous L, LL, and even LLL drop-ins I've had, the low was not much (if at all) lower than the low on the full power M31. I don't think they'll offer you much more run time on low.

That's why I keep the M31 in there. Full power when I need it and insane run time when I don't.