P91 Heat in Nitrolon Body

Just wondering if anyone's tried running a P91 in a nitrolon body, and whether this could cause a violent type event. Either with primaries, or IMRs, but mostly worried about IMRs.

My first Surefire was a G3 with P91 and primaries. I used it on camping trips were I sucked the primaries dry each and every time (18min). I currently use my P90 and P91 lamps in G3 type Legos and they work fine and I dont notice any heat issues on the cells or lamp issues.

bigC

I would worry more about the lense than the body.

IMRs are inherently safe. Their chemistry isn't supposed to go boom.
Also, SF sells the P91 as an upgrade to the P90 in the G3, so I would guess that its SureFire approved (Only when using SF Primaries in a G3 anyway).
Also, about the window. I wouldn't use the P91 in a Nitrolon head for extended periods of time. The window is made of Lexan (think plastic), and the Nitrolon head won't conduct heat away quickly. But in bursts it should be fine.

I have a G2Z (glass lens) with a P91 with 2x IMR 16340. I run it the full 8 minutes and I have done it probably 25X. It gets hot, but it will never melt. Now you might have problems if it comes on in your pocket or if you are running with much larger batteries for much longer runtimes, but if you are just using a G2 (with glass lens) or G3, you won't ever have a problem.

Leukos, that's the same build I was thinking about for CCW purposes.

Thanks for the tip!

I'm pretty sure the G3 head since it came out contains pyrex.

I'm suspicious that the newer G2's (2 years or newer) contain pyrex as well.

One of these days when I take my newer G2's head apart to clean it I hopefully can confirm or deny this.

The G2Z's head contains pyrex.

I've run my G2 with a P90 on IMR's for many hundreds of hours and I've noticed no issues. I know this thread is about the P91, but I only say that because I know some people with lexan heads in older 3 cell Surefires such as the 9Z/9P/Z3 have run into lense melt problems running the P90.

Pyrex, such as the type used in cookware is not a whole lot more expensive than lexan to my knowledge if at all, so I imagine Surefire decided to go with pyrex all around to minimize problems and standardize production, but that's just a guess !

One positive thing about lexan heads, while they are more scratch prone and pass slightly less light, they are much tougher to shock/drops and abuse than pyrex, though the thick piece of glass that Surefire uses is pretty strong. Lexan heads are well suited to a super tough LED light.

The P91 was designed to run off 3x CR123A primaries.

Running it on 2x Li-Ion (LiCo 18500 or larger) or 2x IMR (LiMn) will make the bulb run brighter and therefore hotter. In theory, you would risk over-heating a Nitrolon head, although I don't recall hearing of any incidents where this has happened.

I run the P91 in my G3. Not too long ago, I had the light in a "holder" facing up to bounce the beam off the ceiling. Don't know how new/strong the batteries were, but after about 10 minutes, the light went out.

Reached for the G3, and it was HOT. I could still hold the body of the light in my hand, but the head was way too hot to hold. I opened the light and slid the batteries out. Scorching hot! The glass lens/window was fine.

After the batteries and light had cooled, I slid the batteries back in, and the light worked. So, I assumed that the light had gone into thermal shutdown when the light went out. I could be wrong, so don't take my word for it. YRMV.

R@ndom said:

I would worry more about the lense than the body.

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