I really want to keep the standard look (standard handgaurds) of my rifle.  I see free float tubes by RRA and Bushmaster (I'm sure there are others)

Do these tubes install directly over the barrel and are they solid tubes (like a pipe)?

So the real question is would these be bad in a situation where I want to shoot a multiple rounds, due to heat build-up?  They seem like they would hold in all the heat, unlike most handgaurds which are well ventilated.  

I had similar concerns a while back before I put a Rock River CMP float tube on my Bushmaster.  To answer your questions, the float tube is a solid pipe with the exception of a 3 to 4 inch slot cut in the top near the front sight block to clear the gas tube.  The RRA float tube has three pieces.  First there is a replacement barrel nut, this installs and provides a threaded collar for the float tube to screw on to.  The final piece is a small lock ring that tightens against the new barrel nut and keeps the float tube from rotating and cinches up the threads so it doesn't droop.  

The float tube itself is a great heat conductor.  Standard handguards come with a heat shield installed that prevents air flow through the handguards.  I don't think that the float tube would be any worse in that regard.  It also has much more mass than the aluminum heat shields so it is a better heat sink.  If I was planning on doing a lot of mag dumps I might ventilate the float tube with a series of small holes on the top side to allow some air flow.  

All that being said, air is not a good thermal conductor, and unless the barrel is starting to glow, you don't get much heat dissipation by radiation.  This pretty much means that the barrel is going to get damn hot no matter what.  You can add mass to the barrel to slow heat rise or provide an efficient heatsink (one that makes contact with the barrel) to remove heat.  Water jackets don't work too well on small arms so a heavier barrel is the best option.  Something I haven't seen that might help is to put clamp-on aluminum heat sinks on the barrel, under the hand guards.  This wouldn't add as much weight as a heavier barrel and with cooling fins, like you see on amplifiers, it could help dissipate heat by increasing the surface area.

Yes it will lead to a heat build up and normal handguards especially the double heat shield M4 handguards trap heat as well.  The most effective handguards for allowing the barrel to cool are the railed FF forearms which you seem to not like.

Thanks for the replies. If I do order the BFI or RRA, I assume I need a barrel wrench and probably one of the receiver block/clamps.  Punchs for the sight, gas tube wrench...  anything else?  

Is it really that straight-forward, or is there more to it than that?  Is headspace affected by removing and re-installing the same barrel?  I'm sure it wouldn't hurt to verify.

Thanks

I believe most SIR systems are free floating the barrel and they are design for better air circulation.

My local (only) gunsmith came up with this when I said I wanted to keep the gun looking original. This is a free floated fore end with the heat shields .

Haven't found how to post pictures here, so in the mean time go here for a look:

http://www.water-filters.clara.co.uk/arpic1.htm

The complete rifle cost $1868 (good eh?)

regards

bbutter

here's your pic... very nice looking rig.

[img]http://www.water-filters.clara.co.uk/newbaby1.jpg[/img]

This brings me to another question... how much barrel heat is too much? Is HBAR less susceptable to heat damage?

I have an Yugo M48A Mauser, which I have shot til the cosmo started coming out of the wood and couldn't use the scope from the heat waves coming off the barrel and distorting the view.  It still shoots very well.

That gun cost $100.  AR's don't.

Thanks for posting the picture.
regards
bbutter