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Posted: 3/16/2005 11:51:58 AM EST
I assume someone has tried this, but a search turned up nothing.

Anyone tried coating the aluminum heat shields in the handguards of an AR15/M16 with a ceramic thermal barrier coating?
Link Posted: 3/16/2005 12:02:04 PM EST
Link Posted: 3/16/2005 2:06:55 PM EST
Cold air is supposed to come in through the holes in the bottom, cool the barrel and carry the heat out the holes in the top. A ceramic thermal barrier coating wouldn't change that - it would just keep everything on the other side of the barrier cooler (how much cooler is the question).

There are also black body emitter coatings that are supposed to help surfaces dissipate heat more quickly. Anyone know of any experiments with using those on barrels?

Another thing I've wondered about is using a thermoelectric generator to convert waste heat from the barrel into juice to power a small cooling fan - too complicated for tactical use, though...

Link Posted: 3/16/2005 2:15:12 PM EST
I shoot quite a bit of full-auto, and this sounds more like a solution searching for a problem..
Link Posted: 3/16/2005 2:22:57 PM EST
[Last Edit: 3/16/2005 2:23:38 PM EST by Essayons]

Originally Posted By TheFNG:
I shoot quite a bit of full-auto, and this sounds more like a solution searching for a problem..



LOL I don't disagree, but how much money is made every day here on the sale of such things? Or all the handguards and handguard enhancements already on the market (M4 handguards, DPMS Glacier Guards, ceramic inserts, etc.). If I were not more inspiration than perspiration I might try buyin a bunch of regular handguards, having the shields coated, giving them a fancy name and selling them here. I'm just too lazy
Link Posted: 3/16/2005 2:55:47 PM EST
Just thinking out loud....couldn't you take out the aluminum shields and the coat the inside of the handguards? This would allow more airspace bteween bbl and guards and the ceramic coating would hold back heat.


Nah after I thought about it more the handguards would flex and break it off..correct??
Link Posted: 3/17/2005 6:41:15 AM EST
I hadn't thought of that - you could just coat the inside of the plastic handguards. I read a post on a backpacking forum about a guy who coated the inside of a plastic cup as an experiment (IIRC he wanted a way to keep freeze dried food and water hot while it reconstituted). He filled the coated cup and his "control" cup with boiling water and recorded the water temperature at regular intervals. The coated cup kept the water warmer longer by slowing heat loss through the sides. You'd think the handguards would be stiff enough (minimal flex) to minimize flaking.
Link Posted: 3/17/2005 10:03:36 AM EST
The heat shields are just that.. they are shields. They are bright and shiny to reflect the heat where it will go into the AIR around the barrel, and convect up through the top holes, drawing cool air in the bottom.

The idea is to REFLECT the heat, not allow it to absorb into the aluminum, and melt the plastic. Yes, handguards will get soft if you shoot enough full auto.

Leave the heat shields alone. They are for protecting the plastic of the handguard, and have no effect on the barrel.

A little physics for you... "a perfect absorber is a perfect radiator". This is why heat SINKS are flat black, they absorb heat and radiate it through the blackened fins better than if they were shiny and reflective.

JP makes finned aluminum heat sinks. Helpful hint, if you experiment with this, they should be BLACK, and no other color. A finned heat sink will clamp directly to the barrel, draw heat from the barrel, and radiate it (via more surface area) into the air from the fins.

JP's fins run lengthwise, which is fine for an unvented tube handguard. But for a vented handguard, the fins need to be radial (looking like a series of washers along the barrel) so the air can pass them from bottom to top.

Link Posted: 3/17/2005 10:49:39 AM EST
There's not much above your post that contradicts it. I think we're more or less on the same page.

Based on your input, the best place for a ceramic thermal barrier coating (if any) would be between the heat shields and the outside of the handguard - applied to either the outside of the heat shields or on the indise of the handguards.

My information/understanding of this stuff is mostly automotive - thermal barrier coatings on parts you do not want to absorb heat (piston tops, inside of headers, etc.) and black body emitters on things you want to radiate heat (intercoolers). I already acknowledged that this application is a solution looking for a problem. We're just kicking around ideas here.

Link Posted: 3/17/2005 10:53:59 AM EST

Originally Posted By TheFNG:
I shoot quite a bit of full-auto, and this sounds more like a solution searching for a problem..



+87!
Link Posted: 3/17/2005 11:01:55 AM EST
[Last Edit: 3/17/2005 11:03:47 AM EST by CJan_NH]
The Surefire M500 series of forend weaponlight has dual, Colt M4 style heatshields. The inner pair is solid (no holes), and is coated with some sort of epoxy-like substance. It looks too thick to be standard anodizing, and it scratches pretty easily.

Both pairs of heatshields are removeable, and that could probably be useful with sustained fullauto. With both shields intact there is no air circulation whatsoever.
Link Posted: 3/17/2005 11:28:14 AM EST
I think we're more or less on the same page.

Yes, I think we are.

I just wanted to add a little more info. There is a ceramic product on the market, a moldable ceramic material to put inside handguards they are calling "heat sink", but it is not, it is merely an insulator.

A heat sink draws heat away from one area, and radiates it to another.

A heat shield reflect heat.

An insulator blocks transmission of heat.

Just wanted us to all have our terms correct.

In the past there have been a number of manufacturers who have made handguards without heat shields: Lone Star Ordnance, Olympic. People griped about it, that they were being "cheap", but I never heard of anyone melting one in semiauto fire. With full auto and dumping half a dozen mags, probably.

Cav Arms has pictures of THEIR plastic handguards, no heat shields, but they fired so much full auto (with Beta C drum) that they melted the gas tube. The only damage to the handguard was where the hot tube touched the plastic. Shaun made a point of saying THEIR handguards did not need heat shields, but customers would think they were el cheapos if they did not put them in. And he said all their personal and company test guns did not have shields. That is some good plastic!

Link Posted: 3/17/2005 3:04:23 PM EST
The one place I could see that being beneficial would be on well ventilated aluminum 4 rail handguards. The heat would still be able to move out, and it wouldn't transfer into the hanguards as much. How ever, if you use standard rail covers, it would probably yield no real benefit.
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