I am thinking about getting a carbon fiber tube for my first rifle, as they are fairly cheap and very lightweight. I was going to have it cut to carbine length to match the Bushy superlight I am planning to buy, but I think it would be cool if I could get a low pro gas block and a rail mounted front sight and drill and tap the tube for rails. This way I could have a dissy-sight radius and  could add more rails later on if I want a vertical grip or flashlight. it would also make a fun little project.

I knwo some of you have done this, but I can't remember who. How would this be done? What tools would be needed? All I am worried about is lining up the rails for the front sight correctly so I don't have to compensate on the windage too much. I don't know enough about installing FF tubes to know if that would be a problem.
So, what do the experts say?

Brownell's sells an alignment fixture for drilling into barrels and such (B-Square makes it, IIRC), but I dunno if it'll adjust wide enough to use on a handguard.

The float tube on this rifle is a Jeff Cramblit custom tube.  He used some type of fiberglass/plastic tube with threaded inserts for rail attachment.

A quick search on the internet came up with a little info on threaded inserts:

Threaded insert info

My tube is pretty thick, about 1/4 inch.  The carbon fiber tubes are probably alot less so these might not work.

You may want to go with some type of reinforced rail on the inside of the tube, but it would likely have to be contoured to the tube.

Others have done what you want to do, so maybe they'll find the thread and help some more.

Good luck.

I love that FF tube...how much did that put you out?

I especially love how it's got the original FSB sticking out. How much does it weigh?

I still don't know who drilled into the carbin fiber tube and did rails though, but I knwo he's on the board. Where are you, you sly dog?

I got the tube off of GunBroker a while ago for $100.  The tube isn't light and the whole rifle is very heavy, but I made it for target shooting, not humping through the jungle or the desert.  If was a fun and different project.  I have contacted Jeff Cramblit, the maker of the tube, via email to see if he had rails for the tube, but he doesn't make either the rails or the tubes anymore.

Darn...well the whole point (besides looks) is weight reduction...the Clark's Custom rifle length is 6 oz, which is extremely light. If all goes well, I will either be using a BM superlight and using a low pro gas block and rail-mounted front sight, or just having a 20" barrel cut to 16" and the gas reworked. The second sounds easier, but I definitely want rail options.

If anyone has any expertise, I would greatly appreciate it. I just ned to know what tools and supplies to use. Try this: If you were going to drill for rails, how would you do it? I'm not in the least mechanically inclined, but I'm sure someone can point me in the right direction. Thanks for the posts so far, hopefully more to come.

Please don't take this wrong but if your "not the least bit mechanically inclined" then consider buying a tube with rails already on it. You can easily drill the needed holes but only after you've installed the tube and measured exactly where the holes need to go. It sounds simple but if your drill bit walks just a little or if your off just a tad, your screwed. Buying one ready to go would be the cheaper route. But then again I've done worse things just because I thought "what if?"

I was kind of under the impression that you could just drill two straight holes, and then attach the handguard, lining up the rail as straight as you can. I haven't installed a FF tube but I figured there would be a way to control the position your tube attached...I think I will probably go with a different handguard, but I would still like to try a project like this someday.

What is a good source for the rails them self?

Quoted: What is a good source for the rails them self?

Fulton Armory has a floating handguard with removable rails.  You could get the rails from them, which are already machined to fit a tube of (about, at least) the same diameter.  I'm considering doing the same thing with a fluted alum tube.

I am considering adding some rail segments on a v-match. I want to add a flashlight and possibly a vert. grip. If anyone has photos or advice i would like to see it. thanks.

     I bought a armalite tube and drilled holes to ventalate it.  I drilled some more on top to mount a yankee hill rail.  If you want it real secure i would say get a piece of aluminum bar stock and run a maybe 1/4" piece down where you want the rail to fit.  Then either epoxy it in and drill and thread it from the outside of the tube or you could just put nuts on the inside to secure the rail.  Using the barstock would give a good plate to spread out the load.   major
 

I've never done this but have thought about doing something similar so I've had the same questions.

From reading similar threads it seems like getting the rails set up straight is only half the battle.

Another equally important concern  is how do you insure that the free float tube can be indexed back to the same position.

To my mind it  seems that getting the tube indexed is not just a one time concern; it has to be repeatable.

Like I said I haven't done this myself so I'm curious; is that a big deal or easily managed?

  Thats why i wanted to use the armalite tube.  Be forewarned though the armalite tube is 2 1/4" in dia not 2".  I couldnt find any other fiberglass or carbon fiber tube that was reletivly cheap and could be indexed reliably.  

Here's the procedure I was thinking about.

Snug down your tube
Place the rail where you want it, and secure it in place with tightly wrapped sugical tubing
Use the holes in the rail as a template to drill your holes
Secure the rail with the appropriate allen head screws and nuts

That should work for aluminum I think, but maybe not carbon fiber which I don't have much experience with.

How are the 4-rail float tubes made to index properly every time?

CMMG sells Carbon tubes with any rail arrangement you want on it. Look on their site(cmmginc.com) in the uppers section there is one called the RECON with one on it, They also have a pic of a Carbon Kitty Kat upper.