This is kind of a theoretical, "perfect world," hypothetical question.  We can free float barrels all day long but they're still attached to a gas port/tube.  Apparently, judging from some of the targets posted by some of the builds guy's have done on this board, that's not an issue?   But if you were building an AR, for maximum accuracy attainable from the best (your judgment) components available, built buy one of the pro's, would you include, or omit, the FSB?  I'd like to know because I really want to do it.  But as important, this should, open up a plethora of arguments about who makes the best what, so I thought I'd share.

BCM, I know.

Uou would still need a gas block and tube, unless you want a ingle shot AR.

He's correct you need some method of getting the gas back to the carrier key whether a standard FSB or gas block.

If you're one of those guys concerned about barrel harmonics and unitizing and such you probably wouldn't be posting in this forum.

For precision shooting the biggest factor is the shooter, followed by the ammo. Barrel is down the list and I'd bet that gas block is much further down.

I'm happy with 4-5MOA with M855 out of a M2 red dot at 100 yards. Any functional gas port device change is going to have no affect on that kind of shooting.

I think consistency is the key to accuracy. Free floating the barrel eliminates issues with tension on the forearm from hand/sling/rest concerns. I don't think it matters if you have a FSB or a lo pro gas block, the characteristics of the rifle will be the same shot to shot.

The free float of the barrel is more about eliminating shooter related issues than weapon related ones.

I think you only have to look at what the long-range competition shooters do.  They have all the hands-on trial and error experience.

Long range rifle shooters generally use longer length barrels than I had in mind.  I've read the suggestion that they dynamics affecting shot poi consistency has to do with barrel harmonics, hence the free float, but that the shorter the barrel, the less the harmonic dynamic comes into play.  Which makes sense.  Every one else, I get the gas tube/single shot concept.  What I'm saying is if we can make super accurate barrels functioning from a gas port located on the barrel, obviously THAT's not an issue that screws up accuracy.

I think I'm just going to go ahead and let some builder I like build a SS barrel to the newer heavier M-4 contour, machine it for the M-4 FSB and install it under the KAC.  Actually, I'm wondering if one of the new Colt M-4 barrels would fill the bill, if I could get one?  But the ones I've seen for sale were high, and a custom barrel could eliminate the M-203 shoulder, which makes me nuts.  More nuts.  

Thanks for the input (as always), all you guys.  When I do it I'll get pic's up.

well, the farthure out on the barrel you go, the easier it is to move.  Mayby a pistol length gas system with a pinhole...

Honestly, the regular gas systems are capable of sub 1/2 moa with the right barrel/ammo/shooter combo.    Anything less, you gotta go bolt action and spend $ out from between your hind-quarters.