You won't, EVER, melt a true CF handguard. PERIOD!
Now, some of the "lesser" designed setups like the epoxied in place DPMS factory CF handguards originally shipped with a grossly inadequate epoxy resin that was prone to failing both due to impact and due to heat. DPMS remedied that issue, but the newer epoxy they ship is so strong that once you epoxy the handguard tube to the barrel nut, it is considered permanent because the heat/torque required to remove the unit generally damages the handguard tube.
Quality products in CF like those from PRI, Lancer, CarbonArms to name a few will give you a lifetime of faithful service, even under extreme use/abuse.