Boring out a SF M4 tube for 18650's ?

I want to buy a Sure Fire M4 and have it bored out to run 2 x 18650's. I also plan to put a Lumens Factory EO-M3T (9V, 450 Lumens) Extreme High Output Lamp Assembly in it for an extremely bright thrower.

Is this even feasbile? Can it be bored out for the 18650's? Will these batteries be enough to get maximum output (at 7.2 volts) for this lamp?

This is my first build and I want to do it right before I buy all the parts. Any advice is appreciated.:thumbsup:

Thanks in advance,
Dan
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probably not the walls are not thick enough.. check out light hound for leaf bodies that are made to take 18650's with the m series threads.

I've had some Surefires bored but not the M4. C2/C3 and a couple others I don't remember right now. The problem mentioned by those that did the work was that the o-ring grooves at the tailcap make the final product weaker there because of the decreased thickness. So far I've had no problems even with a C3 and a one cell extension but then I've not been that hard on the light. I don't really crank down on the extension just to be sure though.

-LT

The walls are easily thick enough for boring, it is true that the threads and O-ring area will require some attention (keep both areas well lubricated). Bored SureFire has many advantages over the LeefBody, of which I am too lazy to go into detail. Suffice to say that a bored M4 was used for the following beamshot sessions:

Beamshots: MN16 vs. MN21 vs. MN61
Beamshots: MN61 vs. 1185 vs. 5761
Beamshots: 1111 vs. MN21 vs. MN61 vs. 1185

The M4 powering the 5761 off 2xIMR18650E @ 7.8V) is likely the highest output setup available that can be safely driven (versus M6 + 5761 + 2xC @ 7.4V) in a standard SureFire body. Run the MN15, or an LED TM for good output with good runtimes. Or the MN21, or 1111 (both of which will handily put down the EO-M3T) for very good output with fair runtimes.

The Leef body from Lighthound is a good one.

I have the 2x18650, C tail - M head Leef body. A better solution than boring out an M4.

An alternative solution perhaps, but not a better one. At least not to me. I had two LeefBody tubes in my possession before relieving myself of them over at CPFMP. I was in the midst of searching for posts where I commented on various LeefBody issues, one of which revolved around the tailcap threads interfering with proper electrical connections. But then I remembered that I am supposed to be lazy, so it is up to you guys to do your research before deciding on your own course of action .

Great info and nice beam shots! What is the 5761 and 1111 though?

Dan

adamlau said:

The walls are easily thick enough for boring, it is true that the threads and O-ring area will require some attention (keep both areas well lubricated). Bored SureFire has many advantages over the LeefBody, of which I am too lazy to go into detail. Suffice to say that a bored M4 was used for the following beamshot sessions:

Beamshots: MN16 vs. MN21 vs. MN61
Beamshots: MN61 vs. 1185 vs. 5761
Beamshots: 1111 vs. MN21 vs. MN61 vs. 1185

The M4 powering the 5761 off 2xIMR18650E @ 7.8V) is likely the highest output setup available that can be safely driven (versus M6 + 5761 + 2xC @ 7.4V) in a standard SureFire body. Run the MN15, or an LED TM for good output with good runtimes. Or the MN21, or 1111 (both of which will handily put down the EO-M3T) for very good output with fair runtimes.

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Links directing you to their respective specifications are available within the beamshot threads.

or try using 17670 batteries.

17XXX batteries are 1mm thinner then 18XXX batteries.

aw has them too.

Crenshaw

adamlau said:

An alternative solution perhaps, but not a better one. At least not to me. I had two LeefBody tubes in my possession before relieving myself of them over at CPFMP. I was in the midst of searching for posts where I commented on various LeefBody issues, one of which revolved around the tailcap threads interfering with proper electrical connections. But then I remembered that I am supposed to be lazy, so it is up to you guys to do your research before deciding on your own course of action .

Click to expand...

I've heard of some issues with Leef bodies. Still waiting to get my hands on an M4 head to complete the light. If an issue comes up, I can just sell the Leef body. I know a stock M4 can take 17670 cells. I just prefer the increased performance from 18650s.

Found this old thread as I plan to bore out a brand new M4 (as soon as one is snagged on Buy-Sell-Trade or on eBay).

The problem mentioned by those that did the work was that the o-ring grooves at the tailcap make the final product weaker there because of the decreased thickness.

Click to expand...

I strongly believe that is a non issue. Measure any "standard" Surefire tube, meaning those tubes that have an outside diameter of 1". I've measured dozens, including 3P, 6P, 9P, C2, C3, M2, M3, M4 - all measure in the range of .999" to 1.002", showing that the company holds a pretty tight tolerance on OD.

The area of concern is the outside diameter at the O-ring groove. Measuring all the lights mentioned above shows measurements in the range of .774" - .776"

To fit most 18650's, the inside diameter of the tube needs to be at least .734". To fit every 18650 that I've been able to measure, the ID needs to be slightly larger, at .738". Modders have been boring Surefire bodies out to this dimension (.734"-.738") for years, and I have yet to hear of a single light that failed at the O-ring groove. The walls are still substantially thick (.775" minus .738" leaves .037", divided by two = nearly .019" wall thickness).

In comparison, I've found thinner walls in commercially available tubes. My FiveMega tube (for the 9P) measures .775" OD at the O-ring and has an ID of .750". This leaves the walls about .013" thick, quite a bit less than a bored Surefire, but still practically indestructible.

My current "experimental project" is to bore my personal E2L for 18650. The E-series lights ARE very small to start with, but I believe they can be bored to very closely fit an 18650 and still leave about .013" wall thickness. All experiments are first performed on my personal lights, before this service is offered to the public.

The walls are easily thick enough for boring,

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That's certainly the way I see it. The M4 should present no more challenge than an M3 or M2.

Another option is Pila GL4

I have a GL2 and love it....takes 18650 and 17670 and 2x123 perfectly.

Pila is so underrated.