This isn't an AR15 specific question, but I'd figure I'd see if anyone knows the deal.  I have a Benelli M1 and a Vector V53p (HK53 pistol) with Surefire forends.  I bought 2 Cree bulbs that are 3 mode lamps.

Somehow... they're switching modes and I have NO idea how.  I dropped one into my Benelli forend and it ran great from day one.  When I got the HK53 forend, the same LED style wouldn't work in that forend.  It was REALLY dim.  So I took the bulb out of the Benelli and put it on the HK53, this one went dim too.  I put it back on the Benelli, dim on the Benelli now.  I started swapping out parts, mixing and matching.  At one point, they were both really dim.  I have no idea what I did, but finally one worked in both.  It's like it changed modes.

How do these things change modes?  What gives it the signal?

I think I paid $10 shipped for these two bulbs.  I thought I had hit a gold mine for cheap LED upgrades.    The HK53 forend doesn't actually fit the bulb, it's too fat.  I have to use the Benelli flashlight parts to test out the HK53.  It's just got me stumped.

Maybe I'll post a video later of what's going on.

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Edited to add video:

https://www.youtube.com/watch?v=kcwwpu6bEZ4&feature=youtu.be

First, ditch the cheap Chinese crap and get a Malkoff drop-in: Malkoff LED drop-in.

Second, a weapon light should be single mode ONLY.

Plus 1.
If you are using a Surefire, Lumens Factory actually fits better than Malkoff in 6P/Z2.

Check your driver voltages.
Dim LED looks like you cooked it and it is as good as useless.
Modes switch by turning on and off quickly.  
Gun recoil switches these type of drop-ins quite often.
You need single mode.
You can use a multi-mode in your utility light but don't use it on gun.  Unless you are a criminal that is.

+2

You're saying not to use cheap Chinese crap... but all I've done is swap out a Surefire bulb for a Cree one.  Even the Malkoff says "uses Cree XP-G2" for the bulb.  So I guess it's Chinese crap too?

I'm confused that it changes modes by quick on and offs, as I've tried with this bulb and I can't get it to change back.  I don't see much of a point in spending $40 on a new housing and a bulb (which is the Malkoff kit) when I can buy the same bulb for $10 shipped.  The bulb doesn't fit in my 628, but fits perfectly in the Benelli Surefire light.

I agree that I should've bought single mode only.  Derp mistake on my end.  

ETA - I just checked... these bulbs ARE supposed to be 1 mode...

It's not just the LED itself but what's around it and how its built. The Malkoff is a solid brass heatsink with fully potted internals. That's a big difference from dual springs and a cheapy reflector with the LED and circuitry just stuck in between the two. FYI Cree makes the LED's for most things out there, They make good LED's but china makes some shitty parts to go around them.

Ah, so you're saying the reflector and springs and such are the cheap Chinese crap?

Mmk.

I might limp by with what I've got for now, and maybe just buy the Surefire LED adapters later on, then.  It doesn't appear that the Malkoff conversions are much cheaper than going with a factory solution... but I might be getting confused by what's out there.

^^^^^^

Malkoff is the best that is out there. The LEDs are made by Cree, but the similarities to the chinese drop-ins end there. The Chinese use a thin aluminum reflector and a cheap circuit board that is barely tack soldered to anything. Also, because of the thin metal they use they hardly transfer any heat to the aluminum body of the Surefire so your output will suffer as the LED heats up. The Malkoff drop-ins are shockproof because the electronics are epoxy potted, so nothing is going anywhere, and with the heavy brass heatsink they have much better thermal regulation than the chinese drop-ins.

I had a Thrunite XM-L drop-in a few years ago when Cree first released the XM-L, and I experimented with using it for a weapon light in an M951 (this was before Malkoff offered drop-ins using the XM-L). The circuit board was barely soldered to the back of the metal piece that screws into the reflector, and the solder joints quickly broke with 5.56mm recoil so I had to fix it with a solid ring of solder so it would stay. I wanted something that put out 400+ lumens and Thrunite is considered a "quality" chinese LED drop-in but even it wasn't up to the rigors of being in a weapon light. Save the chinese drop-ins for handheld flashlights.

ETA: Years ago Malkoff's regular selling price was $60 and at that price I bought almost a dozen for all my Surefire lights, both handheld and weaponlights. And at that price you were getting an excellent LED engine that was well worth the money spent. The current prices (around $40 on their website) are an absolute bargain. At the recent prices it's hard to consider buying anything else.

Also, the Malkoffs are MUCH better than Surefire's own factory LED upgrades. The P60L and KX4 do not even compare, the colors suck and the runtimes vs. output suck even more. So there's more to it than simply price or lumens.

This guy went into a lot more detail than me which is awesome. Definitely agree on the bargain portion. The only drop-in I have any desire to try other than any of the Malkoffs are the Elzetta M60. It uses an optic instead of a reflector so i'm curious about the throw and beam configuration on it. Back to Malkoff drop-ins, I prefer the M61W because it has a warm tinted beam which I prefer but that just depends on what you like.

I just wanted the OP to know WHY the chinese LED drop-ins are sub-par, rather than simply say "because they are" or "because I say so".

I have two of the Malkoff M60s with the optic, I've had them since before Elzetta even existed I think, when you could still buy the M60 direct from Malkoff. Anyways, I have a full-power M60 in a Surefire M951 on one of my rifles and the other M60 is actually an M60WL (optic with warm tint, lower output, about 140 lumens with a 5 hour regulated runtime IIRC). I have the M60WL in a Surefire Z2 and it's my favorite light. Needless to say the M60WL was very hard to come by! But the Z2 + M60WL is my favorite EDC light.

I also have the M61, M61N, and M61WL. I also have an older M61W that's pretty nice but then I bought another one and didn't realize they went to a warmer, pinkish LED so I sold it. 4000K is the sweet spot IMO for a true neutral tint emitter and they offer this with the M61N. The newer M61Ws are 3000K and that's too warm for my liking, I feel it sacrifices too much output to achieve the warmer tint.

Yoda, so if I was wanting to upgrade my M951 to LED which current Malkoff would I want? I just picked up 2 more p60's but some more lumens are desperately welcome, as long as it's not at the expense of a 20 min run time lol

I have a Malkoff M61 in an M951 myself and it's the brightest of the M61s at 325 lumens but it's a cool white LED, the tint is a bit sterile/harsh. If you just want maximum lumens that's a good choice, but a better choice in MY opinion is the M61N because of the neutral tint. It sacrifices some lumens (280 for the M61N vs 325 for the M61) but with the neutral tint you can better distinguish details at distance so I would say that despite the lower output you can actually see better with the neutral-tint M61N versus the cool-tint M61. And because I own both I've been able to compare them side by side and they are both so bright that you don't even notice the difference in lumens. The M61N is definitely my go-to LED engine for any P60-based weapon light.

ETA: On every M951 that I've put a Malkoff in I've had to dremel the inside of the collar (the threaded piece that connects the body and the bezel, which the bulb assembly sits in) to make the Malkoff LED fit. It will actually fit without any dremeling but I like for the bezel to screw down all the way onto the collar. There are different generations of M951s so YMMV but all of mine except one are of the newest gen with the skinny bodys like what you see on the M952V. Sounds like a hassle but it really is worth it if you want to breathe new life into the M951. Some people would rather buy a Scout Light or something newer but the M951s are perfectly serviceable and bomb-proof lights, the stock P60/P61 incandescent bulbs for them just suck in today's times. The M951 + Malkoff is the best value in weapon lights IMO, as long as you get cheap, used M951 off the EE.

Thank you sir! I almost bought a Chinese Cree something or other bulb off Amazon the other day, but decided to wait to do more research on the Malkoff, which you just completely did for me. Sucks I won't be able to use my I.R. cap anymore but the run time and output obviously trumps that factor. Gonna pick up one of these and an A.R.M.S. #17 mount when I get payed, then the 951 will officially be modernized

I've seen some cheap chinese IR drop-ins that might be worth trying just to mess around with. Here's one I found on LightHound: Solarforce infrared LED P60 drop-in. I've never used one but I've ordered from Lighthound many times and they are good to go.

Interdasting. Is that one strictly I.R. or it puts off I.R. as well as visible? I might pick one up just for Shits and giggles to see what it does...

Strictly IR.

Thank you for your very detailed posts, Yoda.

It's exactly what I need.  There's four reasons I want to switch over to LEDs:

1)  Lumens/color
2)  How quickly on and off LEDs turn on
3)  Energy savings
4)  Bulb/system reliability

Sounds like these little bulb-only drop ins only give me two of those things, but the Malkoffs give all 4.  With how expensive CR123 batteries are, the small premium is worth it.

Again, thanks for all the info.

Rechargeable RCR123s are great for cutting down the cost of batteries. They quickly pay for themselves over primaries if you use your flashlights a lot so I recommend them for EDC or handheld lights, so you can save your expensive primaries (non-rechargeable) for weapon lights where reliability matters. The only thing is the rechargeable batteries put out 3.7v or more so your LED has to be able to take up to 9v. The Malkoffs can (not all Malkoffs can but the ones talked about in this thread can). But like I said, for handheld or EDC lights, it's like having free batteries, guilt-free lumens.

Good ideas.  AGAIN.  

Don't use RCR123's. 16650's are a superior solution because industrially they are a more common battery size and thus have received more R&D, thus they have much greater capacity, as much as 2500mAh for the 4.35v Sanyo 16650. http://www.mtnelectronics.com/index.php?route=product/category&path=59_88

I did buy a cheap drop-in for the M951 on my 727 clone-ish and the driver eventually died. But it was using an inferior emitter too so I upgraded that as well and now its a direct-driven XP-G2 off a 16650, probably does 600 lumens at first and no circuitry to break.

While 16650's have indeed come a long way recently (I remember that for a long time they seemed to have plateaued at about 1600mAh;) I think it is important to mention that the cells you linked to are unprotected which, especially in a direct drive configuration like you are running, can increase the risks of catastrophic failure if you don't exercise caution with them. Without the low voltage cut off found in most drivers to prevent over discharge you risk damaging the cell and on top of that you do not have the PTC mechanism which is more or less the last line of defense against thermal runaway and the resultant venting/rupture.

But so long as you keep an eye on your cell voltage that hopefully shouldn't become an issue, of course there is also plenty of aluminum in the M951 to hog it out a bit and make room for a protected 3400mAh 18650

^^^^^^^^

That's why I just stick to the protected AW rechargeable cells for my handheld lights. Peace of mind, and not having to worry about such issues. Just run them until the light no longer turns on and then recharge them. As for 16340s vs 16650s, it's simply personal preference, I like the size of the 16340s.

@ Matchbook, that light on that rifle is my HD gun, the light isn't turned on near often enough to seriously deplete the battery. And true, I'd be better served with a single-mode 105C driver or similar but this was the easiest way to get it functional. But you're right, for something frequently used a level of protection is a must. And my 951 is the narrow-tube one, its too slim to mill out for a 18650 or I'd have done so by now.

@ Yoda, It is a nice form factor. But they're not much smaller than a 18350 and for a short light I'd rather the extra capacity.

@nightshade

I guess the other benefit for your application then is the fact that without the protection circuit or standby parasitic drain of a driver you will cut the self-discharge rate pretty significantly. Bummer about the thin walls on your M951 though.
I have always wanted to craft a truly custom weapon light, either machining out or starting with something like the Oveready shaved and bored 6P body and attaching Scout style mounting posts -not only would you get 18650 and P60 compatibility but at about half the weight of a Millenium series light and with the smaller and lighter Scout mounts to boot.

These babies (Sportac P60 LED 1-Mode Module) will wear out the retinas pretty quickly...

Illuminationsupply had some that are protected in 16650.  I have 3-4 but even if you use the unprotected ones the light will get much dimmer before it reaches the 2.5v min of the newer 4.3 max cells.  With Malkoff the light drops out of regulation at 3.4 and starts dimming.  

This will not hold true using two rechargeable cells together as they don't allow the light to drop out of regulation.  Malkoff M61SHO uses two cells but probably wouldn't make that good a light for weapon anyway and it sucks power too fast for general use.  

Illumminationsupply also has Malkoff http://www.illumn.com/flashlights/flashlight-bodies-bezels-parts-and-dropins/malkoff-devices-m61w.html   80 High Color Rendition Index.  I think it was illuminationsupply that used to have the 92 HCRI XPG.  I purchased one some time ago and purchased a pair of the same XPG LEDs. I had one put on a C Mag conversion by Malkoff and kept the other for future use.  I also found a Quark with the same LED put in by the former owner before I purchased it.  I showed a Cabela's store employee saw the light and was sure it was incan.  I couldn't even get him to bet me my 100 dollars to his 1 dollar that he was wrong.

I use a couple of offset PLS-1 mounts because they can be slid off rail by releasing spring loaded catch and still be used in a somewhat modified Roger's Grip with the mount fitting in the palm of my hand.  They are only about 40 bucks and Fleet Farm Supply here has them.