I want to stretch a section of rubber innertube over my alum freefloat tube - can anyone recommend the size tube I need?  I was thinking about one for a mountain bicycle

I'm not sure but I've never heard of this mod, I'd be worried about maybe the rubber melting after a lot of sustained fire.

Just my .02 cents

Not sure if it is an issue at all

I did it to my aluminum tube. It seemed to be fine. It protected the aluminum from scratching, and is quite comfy too. I never had a problem with the heat. But I never dumped mags through the gun either.

I used standard mountain bike tube 1.75-1.95" if I remember correctly.

I have seen it done once before a couple of years ago, and the guy said he had run as many as two 30 round mags thru his with no melting; and besides I mainly use this AR for target/varmint work.  Its basically a poormans Hogue Foreend freefloat tube.

thanks ridge

From another thread..the hogue guard can apparently melt under heavy use.  This came from a Hogue rep. I think.  Can't find the thread but anyway.  Since your not blowin' through mags it shouldnt be a problem but possible.  I would say mountain tube as well.

Righto Horik, I remember reading that post also. I believe it was in reference to putting a Hogue on a full auto, or major rapid fire.

For normal applications it will work just fine as it did for me.

Found it:

mayes,
Brownells carries a sleeve that is hard rubber that slides right over the tube with a snug fit and I'm sure is designed not to melt, call them or I can get the part# for you let me know. I have a dubble bicycle tube on  my mid-length ff tube and it was a bitch putting it on and took me a couple of hours and is very comfortable . Will it melt during 'sustained rapid fire' whatever that is ? I like to let it loose once in a while but 'sustained rapid fire' like in a cq battle 200-300 rounds or more in 5-10 minutes or less ?? I couldn't tell you if it will melt I have never been in a fire fight and does not sound like something I would recommend if I could relate to it . I am aware several of you all out there have been in a cq battle , not to poke fun. Most barrels get very hot after a magazine is exhausted with a 3 count between shots ,but even so the innertube which was from a kid's dirt bike type of tire did not melt and I tried .