Heavier barrels heat slower but government profiled barrels are lightweight under the handguards. Why not just make barrels lightweight? Government profile is also front heavy. What gives?

Nowhere near as heavy as a heavy barreled rifle. I don't find them front heavy at all.

Barrels need to be stiff and thick enough to maintain accuracy and prevent the barrel from over heating. They are profiled according to their use. Military uses a Government profile to reduce weight. These barrels are also chrome lined for durability. Varmint barrels are generally heavy barrels or bull barrels for increased rigidity which leads to optimum accuracy.

heavy barrels heat slower but cool slower as well.
lightweight barrels heat faster but cool faster as well.

the heavy part of a Govt profile barrel helps reducing muzzle climb during firing I think.

IMO, the govt profile bbl is a bad choice for any application. The correct A1 profile is the better choice. The govt is just wasted weight past the front sight base. ColdBlue over at knight's armament has posted here a few times over the years that the govt profile bbl was a mistake.

If you are really interested in accuracy over the utility of the light bbl, I would consider a medium profile bbl that is approximately .750" the whole length, but I would not go any heavier for 5.56mm.

The A2 .gov profile wasn't about heat or barrel whip or anything like that.  It was a response to fears that using the bayonet improperly could damage the rifle barrel.  That's why the front of the barrel was made thicker and under the handguards was left alone.  It was just pure dumb-assery that the rest of the barrel wasn't beefed up slightly.

I like the feel of a Recon profile barrel, gov't under the guards and apprx .750 in front of the FSB.

I couldn't find a Recon barrel a few months ago so I got a Denny's Operator and had Adco lighten it behind the gas block. I think it balances very nicely!

?
That describes a gov profile bbl.
A-1 .625" under handguards
.750" under the FSB out to the muzzle

this... adding material to the front helps nothing.  for accuracy, heavier under the HG would be optimal.  During vietnam, soldiers would use the bbls for prybars and bend them so they beefed them up where they would bend, in front of the HG.  Then added a cut for the m204.  Accuracy wise, a govt profile will perform the same as a LW.  

If u want to shoot a lot and keep tight groups, get an hbar or flutted bull... if you want a light gun get LW(groups will open up if you get the barrel hot). for compromise, get a socom profile.

I was under the impression that gov't profiled barrel is turned down the way it so that it will be compatible with the accessories typically fielded with these weapons. For example, the M203 notch, and the step behind the FH for compatibility with certain suppressors. The lightweight profile under the handguards is just that, a lightweight profile to cut down the weight as much as possible where it is possible to do so.

Theoretically, a heavier bbl. sans the M203 cut is more rigid thus allowing less whip which = better accuracy.
However, my BCM near Gov. profile shoots with my RRA Hbar if not better, probably better.
Anywhere but the bench the Gov. profile will outshoot the Hbar because given the choice thats
the only one you'll want to carry.

Unless you're shooting for ultimate long range accuracy, or mounting a grenade launcher, a lightweight profile barrel is the most practical set-up.  Accurate enough for most anything you'll likely encounter, and lighter to carry.

 

There isn't a reason other then Uncle Sam screwing up yet another thing.  Either go LW or HBAR.  Again, no purpose for the gov't profile.  And as far as accuracy is concerned, with the right shooter and ammo, "most" ar barrels are capable of MOA accuracy regardless of the profile.  I hate that they make so many gov't profiles and it's so hard to get a LW profile.  Chaps my a$$ actually

The light profile under the HG was kept so the M203 wouldn't have to be modified to fit an A2 rifle.  It mirrors the A1 profile where the 203 connects.  Likewise the step on an M4 barrel was an end-around to keep from having to modify too much current inventory.  Its much easier to write it into a spec and let Colt deal with it than to send thousands of grenade launchers off base and out of armory control where they might be "misplaced".

Someone should IM cold blue about this.  It seems like there was a thread a while ago, and he explained how it came to be.  It seems like it was due to an error that was made involving measuring wear in barrels, and the govt profile was the solution to what was thought to be the problem.  He was actually involved in the testing, but I don't remember the details.  

I could also be wrong, and be thinking about something else.  I looked for the thread a few weeks ago, but couldn't find it.  Anyone else remember this or have a link?

Yes, the A2 profile and regular M4 profile are just plain stupid.  When the M16A2 was adopted, it was claimed that the heavier front section would prevent damage from soldiers doing stupid things like using rifles to pry open shipping crate bands. That's a pretty fucked up thing to have to admit that we can't train our soldiers not to do stupid stuff like that with rifles. The standard profile under the handguards was kept for M203 compatability. Now, when a soldier does something that would bend an A1 profile barrel, the barrel  bends behind the FSB, or at the forward M203 cut on the M4. The only possible positive to the thicker front section on the A2 profile that I can see is that service rifle competitors can have a heavy barrel and still meet external profile rules. What is now known as light weight profile, should be known as "standard weight".  What is now known as the A2 (AKA government) profile should be known as the "pointless extra muzzle weight" profile. What is now known as the M4 profile should be known as the "pointless extra muzzle weight with an additional weakening cut because we couldn't imagine having to update or replace the M203" profile.

Would it make sense to have the front of a government profile barrel tuned down by adco? How much would it reduce accuracy and how quickly will a lightweight barrel overheat compared to a HBAR or gov't profile barrel?

They try to shave weight everywhere as possible. Light infantry is anything but light.

I had ADCO turn a govt. profile down for me, to a full lightweight profile.  Accuracy was not affected in the least.  I'm not even sure you could shoot fast enough to "overheat" a semi-auto.





 

I guess I could've explained it a little better but this is essential my profile. Close to gov't but not quite. Or am I mistaken?

My Colt 6721 HBAR always shot MUCH better than my 6520 LW.  On the other hand, The profile of the 6920, or the government profile with M4 notch, was indeed a stupid solution for keeping compatibility with M240 and other attachments.  The way to do it would have been to do what Noveske/FN did, come up with the profile that has the right weight, then distributes that weight in the right places.  Then change the way you attach the grenade launcher.

Denny has a good solution with his Operator; likewise Adco had a good setup, don't know if they are still doing that.

People are always interested in my A1 barrel on my A4 clone at the range or the few times I had it in the shop.  Have received positive compliments on the lightness.

I don't shoot past 100yds, but it has always been accurate.  Heated up quick but I rarely shoot more than 200 rounds per range trip.

The M4 and other guns with the gov profiel barrel that I have shot, balance noticeably different.

I was thinking about changing it to be more "authentic", but I think I like the pencil barrel.  It is a nice FN Chome lined barrel.  No idea on the twist.

I kinda like the profile Noveske used for the N4 Light Carbine barrels- slightly heavier than govt under the handguards, slightly lighter than govt forward of the FSB, but the same weight overall for anicely balaced and rigid profile.