I have noticed that there is a noticeable group of people on this board who prefer a thin profile, or pencil barrel as opposed to a bull barrel or HBAR configuration.

I am from the "old school" and prefer a substantial barrel for a couple of reasons. First, I feel that a heavier barrel is inherently more accurate because barrel whip is more controlled in a thicker barrel configuration. Second, thicker barrels are less likely to be affected by heat and external stress, like that applied by the sling when shooting with one. Finally, I like the feel of a "substantial" weapon. I don't like my weapons to be light and plastic feeling. This is a personal preference and probably stems from my upbringing in which a "real man's rifle" had to weigh 9 or 10 pounds in its basic configuration.

So with all this said, why do some of you say that thin barrel profiles are making a comeback? What are the advantages of these thin barrels over an HBAR or bull barrel, other than weight?

I have built three rifles, 2 of which have heavy barrels and one has a thin profile match barrel (selected due to low price not by profile). A fourth project, DCM rifle is in the works and the barrel I have for it is an HBAR 1/7 20". I know that this thread will evoke a lot of personal preferences, but please explain your self.

I too was an HBar man for many years for many of the reasons you listed.  But recently I got a ff rail forend and started to put a lot of stuff on my rifle and it quickly became very heavy so I had my barrel turned down.  I must say I have quickly come to like the lighter barrel because it swings and stops quicker.  With a heavy barrel it is easy to swing past your target.  It takes time to slow that barrel down once you get it moving.  A lighter barrel stops on a dime.

Many of the problems you listed about light barrels can be helped by free floating.  Barrel whip, while still present, is more consistant because the barrel is isolated.  Also external stress is no longer an issue with a ff light barrel.

Heat is still a problem, however on a combat weapon heat does not affect PRACTICAL accuracy.  Millspec ammo, crome lined bores, 5.56 chambers, stock triggers, shooter skill and stress /fatigue are all more limmiting factors to practical accuracy than is heat induced point of impact shift.

Keep in mind I am talking about a duty weapon, not a target rifle or a even a marksman's rifle.  HBars may still have their place in such applications, but on a general purpose fighting firearm I think lighter is generally better.

i have a pencil barrel on my franken-ar, its okay, but not thrilled with the heat, so my next barrel will be custom, itll be fat completely under HGs and thin under site post and out to the end.

My duty rifle is a Colt AR15A3(HBAR), and with minimal gear on it, it is still a pig.  I am debating swapping it out for a M4 profile barrel.  

Clearing large buildings (factories or schools) gets tiring, and realisticly the weight is more important than the barrel heating up for me.  

All said, I still love my porker AR, but I am debating a diet.

"OLD SCHOOL" is SP-1, NOT HBAR! I like the M-4 profile for the same reasons listed above. Quicker to get on target. Also, have you ever lugged a 20" HBAR with tac light, A helmet, LBE, 40-70lb ruck for great distances? I'll bet you too would apriciate anything that is lighter and still functional.

What happens when you free float a barrel like the bushmaster A2 government profile barrel...Since it is skinny in the middle and fat on the end, would it be unstable and whip around, or is it stiff enough to avoid sagging...

Is it even possible for the handguards to provide support for the barrel?

I'm in the process of building my first AR and would like to get this lightweight barrel, but am not sure how well it would free float.

Would a fluted hbar be better, with a 20% weight reduction?

Thanks.

[size=1][b]"OLD SCHOOL" is SP-1, NOT HBAR! I like the M-4 profile for the same reasons listed above. Quicker to get on target. Also, have you ever lugged a 20" HBAR with tac light, A helmet, LBE, 40-70lb ruck for great distances? I'll bet you too would appreciate anything that is lighter and still functional[/b][/size=1]

"OLD SCHOOL is the first weapon that I carried with any frequency which was an M-14 issued to me by the Dept of the Navy (first in the Marine Reserves and then with USN active duty). It came with all the accessories available including the ones listed above, and the ammo was free. Yes I do appreciate the lighter rifles, even though the HBAR's are heavier than the M-4's, they are both much lighter than what I first carried.

Lighter guns carry easier, swing between targets quicker and are easier to cover a target (read BAD GUY) for a longer period of time.

H-bar on a bench gun is a good thing.  On a mobility gun, IMHO, it isnt.