I know about all the major tubes out have holes all in them.  When you do a lot of shooting through a DD or RAS or YHM, does the heat radiate straight to your hands through the holes or does the rail itself heat up first?

How much shooting does it typically take before your hands start to get a lil warm.

I have a YHM standard free float (not the light weight version).  The bottom three rails protected by magpul rubber guards, the top rail by a magpul ladder guard.  I live in Las Vegas where it is normally pretty hot anyhow, and assuming you dont leave the rifle sitting in the vegas sun for any extended length of time, i have not found a shooting situation where it has gotten hot enough to be uncomfortable.

It will warm up, but just warm, not hot, and the heat tends to radiate upwards out of the top vent holes.

It's basic physics.

The heat gets aborbed into the barrel steel, then is transferred to the air around the barrel.  If you don't have vent holes then there's no where for the hot air to go.  The heat has to be absorbed by the handguards then transferred out to the outside air.  This is also a very inefficient way to get rid of heat because it has to be transferred between several different materials.

If you have vent holes then the heat gets transferred to the air around the barrel, then the hot air rises out the vent holes in the top of the handguards and simply drifts away.  The handguards aborb a little heat from the worm air as it rises out but it is actually not much.  It is also more efficient at getting rid of the heat because the heat on't has to be transferred from the barrel to the air.

Quoted: It's basic physics. The heat gets aborbed into the barrel steel, then is transferred to the air around the barrel.  If you don't have vent holes then there's no where for the hot air to go.  The heat has to be absorbed by the handguards then transferred out to the outside air.  This is also a very inefficient way to get rid of heat because it has to be transferred between several different materials. If you have vent holes then the heat gets transferred to the air around the barrel, then the hot air rises out the vent holes in the top of the handguards and simply drifts away.  The handguards aborb a little heat from the worm air as it rises out but it is actually not much.  It is also more efficient at getting rid of the heat because the heat on't has to be transferred from the barrel to the air.

Thanks Hoplophile.  I was really just curious about what effect radiation would have on hands.  I know that convection works to help cool the whole assembly down when you have holes in the free float tube, I just got worried that the radiation would heat your hands up. The fact that regular handguards have the heat shield made me think they had a major role in keeping the hands cool.   So my next (second) build is gonna have a Clark/Hiperform fiberglass tube and I am gonna drill holes in it for cooling.  I was just worried the holes would let the radiation go straight to my hands at first.

nothing a vertical grip wont fix

I drilled a bunch of 0.50" holes in the solid aluminum tube on my 16" gun.

BIG ass difference in comfort during rapid fire.

Luck,

SD