We’ve all seen the destructive full-auto testing of the M4 vs the M4A1, and how the extra barrel mass under the handguard allows the A1 to take significantly more sustained fire before failure.
My question regards how having a FF tube affects a rifle’s ability to take sustained fire. Normal handguards are plastic (glass-filled nylon, or whatever it is), which is a very good insulator, and they don’t allow much air flow. Many FF rail systems provide for very good ventilation (the VLTOR CASV and VIS systems specifically come to mind), and aluminum is also a good heat conductor. Does anyone have any experience or data as to how a rail affects the rate at which a barrel heats/cools during firing, as opposed to a traditional handguard?