I regularly get asked about how well our handguards will withstand heat and why we don’t have a heat sink. I have class III SOTs building with my handguards and haven’t had complaints. Some of them have told me that heatsinks are over rated and once they are hot then all bets are off.
The Yugo M85/M92 handguards we sell are made from molds cast from the originals, which are very thick and our traditional M70 handguards are the same way. You have to shoot a firearm quite a bit to heat the barrel up and then heat the special high-temp urethane and glass fiber composite all the way through before it will soften. From a technical specification perspective, the manufacturer says the base urethane, without the glass fiber reinforcement we add, has a technical temperature deflection spec of 257F, meaning it will not deform until past 257F.
To test this, I took one of our black gas tube covers, a digital IR thermometer and the oven we use for curing plastic.
At 70F, our cover was rigid and the East German cover could flex a bit. I started the oven off at 200 degrees and kept checking every 15 minutes and the East German cover started to soften first. At 250F, the East German cover was very flexible and at 300F I could almost get it to touch its sides together. Our’s was starting to bend some.
By the time we reached 437F, the East German cover was melting like a stick of butter while our’s was very soft but did not melt.
At 437F, notice how the plastic knife melted when I touched our gas tube cover – it couldn’t penetrate it:
The cover was soft but it then hardened again as it cooled off. I then sprayed the oxidized looking urethane with WD40 and it brought it back to more of its original color.
Maybe the best answer I can give to folks asking how our handguards have held up – we’ve sold hundreds of the M85/M92 handguards and we haven’t had any complaints that they melted or did not hold up. If you search on the Internet, I don’t think you will find any reports either. But with that said, I do have to remind folks that all materials have a limit. If you start dumping drum after drum while bumpfiring or going full auto and the barrel is literally red hot, no handguard is going to survive that without being damaged or even destroyed. That is the only reason we do not warrant our handguards against high-heat – we know there are limits and we know there are guys who will push past those limits. For most people, our handguards will work just fine. I use them myself and have never had a problem with my family and friends at the range doing target shooting.