AR15 carbine handguard materials

Claven2

Claven2

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Quick question:

What materials are the various M4-type hangaurds made of? I'm not talking about Magpul MOE handguards or rail systems, those are obvious. I mean the differences in the plastics of the standard and fatty M4 handguards.

For example, in front of me, I have two similar looking M4 handguards. One set is a black single-shield set off a Colt Canada C8 in black. It does not feel like typical plastic polymer and is more like compression-molded thermoset plastic. Another set that is visually similar is clearly made of what I would class a "lesser plastic", injection molded of polymer or HDPE with a more textured finish but with an obviously greater amount of flex. It's lighter and the heat shield is not as well held in place as on the Colt made part. It came off a Model One Sales upper, if that helps.

All this to say, of all the examples I've looked at beyond the two cited above (because I have them right in front of me, disassembled, today) there seems to be a big difference in the type of plastic used in M4 handguards, the quality of the moulding, and the quality in how the heat shields are retained inside.

The other thing I noticed is that C8 handguards do not fit a standard AR15 delta ring without being relieved a little on the rear lips. Presumbly the Colt Canada military C8 has a slightly larger inner diameter??

Is there a good resource out there describing the different handguards, who makes them out of the best quality materials, compatibility, etc.?
 
You've guessed correctly on the C8 handguards, they're made from some kind of thermoset plastic. They are a ##### to re-install even on the issued guns, lots of times it turns into a two man job.

I do know that CavArms makes their handguards from glass filled nylon 6, as for other manufacturers.......
 
Well I think I've got install and uninstall down to a science, but the fact remains, I had to file about 1/32" off the rear of the handguard lip outer diameter all around the handguard to make it install on a commercially purchased delta ring.

Do C8's leave Colt with a slightly larger than typical delta ring in terms of it's inner diameter? I have to believe yes, as on these Colt HG's, the delta ring would not even begin to close on the Colt units prior to relieving them.

I used a sandpaper-wrapped file, polished the relief to 800 grit and it now looks like it left the factory that way.

These thermoset handguards look visually a lot better than commercial handguards and feel a lot more ruggedly made. The heat shields are also of higher quality and better fitted and secured in the handguard. I like them. No need for anything better unless I wanted to mount a VFG or something. Not much point on a 10" AR in 9mm IMHO.
 
ok, here is an example of how the Colt Canada handguards had to be relieved to fit into my commercially purchased delta ring.

DSCN2569.jpg


You can see the relief "step" about 1/16" in front of the forward edge of the delta itself. The handguard is fully seated into the delta and the ring seems to be as forward as it will go. Before relieving it, the handguard would not fit into the delta ring AT ALL. It was actually proud of the outer diameter of the delta ring. Commercial handguards were fitting this delta ring just fine though.

Makes me think some Colt Canada guns must ship with an oversized ring??
 
As has been said, hand guards are supposed to be made of thermoset plastic because of strength / rigidity and extremely high heat resistance.

I have no idea why the Canadian Colt hand guards would not fit your delta ring.
That is quite a bit of material to have to remove, .03".
 
Last edited:
liberal-hater said:
As has been said, hand guards are supposed to be made of thermoplastic because of strength / rigidity and extremely high heat resistance.

I have no idea why the Canadian Colt hand guards would not fit your delta ring.
That is quite a bit of material to have to remove, .03".
Click to expand...

I totally agree that thermoplastic is a much better material - especially if the gun will see full-auto.

That being said, I've tried these handguards on the following Delta Rings now:

1) Model One Sales
2) RRA
3) Stag

It would not have fit any of these without being relieved.

Is the Diemaco C8 made with a larger delta ring??
 
You have me curious, might have to take some calipers to work.

I was going to say your slip ring could be out of spec but you've obviously factored that one out.
 
I have C8 handguards and they fit fine on a Spikes and 2 different Stag uppers. It sounds like the handguards are the problem, not the delta ring. Did they come off an actual C8?
 
Yes, supposedly. I got them in the EE and they were sold as early C8 Colt Canada (Diemaco) handguards. Every other handguard set I have is a little smaller on the aft end than these ones were.

I have to admit though, apart from this small dimensional anomaly, they are BY FAR the best made set of handguards I have ever owned. The heat shield is very well retained, better shaped than most, and the Thermoset Plastic is far and away more rugged than most of the handguards you buy from third-party sellers. It feels like Early M16 furniture in-hand.

In any event, I like them so much that they are going to stay installed now that I got them to fit. They just feel so high quality compared to every other set I've compared them to.

If I think of it, I'll post a pic tonight of the interior. Also, on many M4 handgaurds, the sides clip to each other with little round stubs. On these ones they are long slots with a corresponding tongue, two per side.
 
I was just browsing the RRA website and they offer Thermo Mold handguards now, but only in rifle length in combination with a freefloat sleeve.
 
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