Attaching a light to a railed gas block? Too hot?

[LigerNoir]

P/S,

I was wondering if it would be doable to attach a weapon light (such as a surefire scout light, x300, or xc-1) to the 12 o'clock of a railed gas block (PRI/YHM as examples) or if the heat generated would be too much for the lights.

Additionally, how much heat is transferred to a barrel mounted option such as the Canadian system for their C7s and C8s.

Thank you!

 

[jBravo3]

Definitely not an optimal set-up of course - IMO. An X300B or scout would survive, but I don't think it's a good idea to cook batteries no matter what - whether or not they're wrapped in polymer or aluminum. How long the lights/batteries survive would depend on a lot, but it's just not an optimal, professional, viable option - again, in my opinion.

If possible, it'd be much better just to put on a low profile block and free float over the top.

I have no experience with C7/C8 so can't chime in there.

 

[shoobe01]

No science behind it, but before I went to an actual floated railed handguard — long ago — I had one of those FSB bolt on mounts, and put lights on it. Got into plenty of "fights" (blank fire mostly, FOF) where the gun got plenty hot, and it presented no issues I noticed with the light mounted.

(Note I DID get failures from other items at the same timeframe. For example I did this solution because I had tried one of the plastic rails bolted through the vents on a normal AR handguard and the plastic rail was soft enough that when I got tangled in some brambles the light popped off.)

I am sure a rail directly on the gas block would be hotter, but if you don't rapid fire too much it might not be a disaster.


I have other thoughts but... it would be first good to know why you are doing this as well. Is it an issue gun so you can't change it more? Will the light be allowed there also, what other things can be bolted on, etc?

 

[shoobe01]

Edit window expired. Another one-off datapoint: I once had to (live) fire so much (about 5 minutes of a full mag every 30 seconds or so) that my floated handguard got too hot to handle. Should have brought gloves, but I just used the 6-o'clock mounted X300U as a "vfg." Worked fine and never got hot at all. Dunno if they are insulated or if just the extra mass and floating out there protects it.

Might be good to just ask Surefire if they have temp specs for the mounting point; they might have thought of this (it has to have come up for another agency or army) and can advise directly if not a trade secret or something.

 

[LigerNoir]

Without any fluff, the why: I like the simplicity of adding a light/laser to the 12'oclock with a car-15/m4 two-piece handguard.

With Fluff: My National Guard commitment recently ran it's course and I am looking for a replacement to my M4 spec'ed 6920. I was able to do some of the cool-guy drills as an IBCT Staff Officer with a very heavy and unbalanced M4A1 that probably weighted 10lbs loaded (PEQ-15a, CCO, Magnifier, Light). I loved the capability of that carbine, but it was unwieldy during indoor drills and split times were abysmal. I'm looking for ways to lighten the load while keeping some of the capabilities of that carbine. I am also a fan of the M4 handguard and have recently removed the KAC rail on my 6920 and put the two-piece back on.

I am uncertain if this will be my answer, but discussions are fun and save money.

 

[shoobe01]

Ah... then I would look into some of the handguard rails, since lights don't need to be zeroed. I just cut one up for an experiment (as it was easier to prototype on than aluminum!) so can't send you the spare I had, but they are zero impact, reversible, no longer the heat worries, etc. Examples:

Plastic, FAB Defense one. Weighs negative ounces, rigid, Seems ovrall decent, but a tidge oversized for true Picatinny, I think on purpose for railgrabbers to hold better since it's plastic.

Aluminum: GG&G UFIR, which is for "under forearm" but they are symmetrical, you can put on top also.

IF you don't need 12-o'clock, always sorta pined for the 1:30 Surefire weaponlights, various folks like GG&G make a tiny rail with grooves to fit on that part of the handguard.

Yes, requires drilling but handguards are cheap and it's two tiny holes even if you take it off. I have used this and there is a common plastic rail for the same which has failed me under stress so I do not suggest.

 

[jBravo3]

TMC Scout Light MOUNT-N-SLOT

www.impactweaponscomponents.com

My dept. has fielded these on most issued patrol div. rifles for several years with good success, zero problems, sample size of about 60. May be a better option for the setup you're describing.

 

[LigerNoir]

TMC Scout Light MOUNT-N-SLOT

www.impactweaponscomponents.com

My dept. has fielded these on most issued patrol div. rifles for several years with good success, zero problems, sample size of about 60. May be a better option for the setup you're describing.

I was in the process of replying when you posted this with this in mention. I actually have this on my 6920 at the moment and it serves it's function quite well (albeit at a slight angle downward thanks to have the Colt M4 Handguard is designed).

I did a bit of internet digging to see temperatures of how hot a gas block can get with a basic string of fire. 450F is quite hot and shoobe01 probably got it hotter in the situation above. Interesting that the x300 was cooler over the handguard.

 

[LigerNoir]

I think I found my answer in a decade old ar15.com post.

Quoting the important part which is a reply from LaserMax about a product of theirs:

"While doing some testing on heat capability we put a Red Uni Max in
an oven at 350 degrees for 1.5 hours. They forgot it was in there. They
brought it to me on an oven mitt and within a few minutes as the batteries
cooled to operating temperature it began working again. Not a recommended
test.
It, as all lasers are limited somewhat by the batteries they use.
Exceeding the limit won't destroy the laser (within reason) but it will stop
functioning. Upper limit is 140 degrees."

Also, correction on heat, 300+F, not 450. Also Also a laser, not a light. Either way, I think my answer is clearly a NO.


- https://www.ar15.com/forums/ar-15/Weapon_light_to_mount_on_gas_block/20-525587/