I see there are two basic m4/R4 profile barrels --thin and thick under the hand guards

what is the advantages of one over the other?-- besides the obvious weight which I see as slight.

In my case they would be ordered chrome lined either way


RRA is thick


the bushy and others are reduced

Most M4s and M4A1s are thin under the handguard, a few use a slightly thicker portion under the handguard.  

yes, but is one better than the other?

I would think the heavier one would be better --being stiffer and able to handle the heat better

Neither

A better question would be "Why do I need an M-4 barrel?"

Unless you are going to mount an M-203, there is no reason.

So, a better question would be "Should I get an H-Bar or a Superlight?"

I've always been more concerned with any negative effects the barrel getting fatter outside the handguards would have.

If you look at all the benchrest rifles, they start thinck then thin out towards the muzzle. I guess I always assumed that doing the opposite would be detrimental to accuracy.

Anybody care to explain why I am right/wrong?

Quoted: I've always been more concerned with any negative effects the barrel getting fatter outside the handguards would have. If you look at all the benchrest rifles, they start thinck then thin out towards the muzzle. I guess I always assumed that doing the opposite would be detrimental to accuracy. Anybody care to explain why I am right/wrong?

Every other barrel in the history of barreling starts thick at the chamber and gets thinner near the muzzle...except for the "Government" profile M-16A2/M-4.

The tomfoolery behind this noonsensical profile has been covered in depth here.

I have a Colt SOCOM M4 barrel that I like a lot.  Personaly I like the hevier barrel.  If  the weight is at all a concern,  I think a 14 1/2"  SOCOM barrel weighs just as much as a 16" lightweight M4 barrel.  If you don't mind sacraficing 1 1/2"  of barrel and getting a flash hider perm pinned.

P.S.  Can't wait for that rifle!

I think the full-auto guys prefer the heavy under the guards profile for heat and subsequent shot purposes.


sic_ness......it seems AR/ M16 set ups tend to use a weight forward - coincidentally for the same reasons as above........follow up shots.

I like lighter under the handguards.  But for a carbine length barrel, there isn't going to be much advantage with a lighter barrel.  If you decide to go midlength or rifle length, lighter is better...

Quoted: Neither A better question would be "Why do I need an M-4 barrel?" Unless you are going to mount an M-203, there is no reason. So, a better question would be "Should I get an H-Bar or a Superlight?"

Well that does bring up a good question:

I just finished putting together my RRA lower w/ two stage trigger minus the stock and now i am trying to decide what to put on the top of it

I have a mid length 16 inch and a 20 inch varmint bull barrel already and now i was thinking of getting an M4 or a NM RRA upper --still searching my soul

P.S. look like I derailed my own thread

M4 barrels are light under the handguards and the selector switch on an M4 is safe-semi-burst.

M4A1 barrels are heavy under the handguards and the selector switch on an M4A1 is safe-semi-auto.

The reason for the different profiles is due to the heat that builds up when a gun is fired full-auto.  If you take a light barrel and shoot 5 shot groups rapidly on different targets you'll note that the groups will be about the same size, but each group will have a slightly different point of impact.  This is no big deal in combat, as you're shooting a man, not a small bullseye.

That's not to say that a lightweight barrel is bad.  There's nothing wrong with one of them, but they heat up more rapidly.  What might be interesting is a heavy barrel profiile that's fluted.  As far as I know no one makes one, but it would be interesting to see.

Quoted: M4 barrels are light under the handguards and the selector switch on an M4 is safe-semi-burst. M4A1 barrels are heavy under the handguards and the selector switch on an M4A1 is safe-semi-auto. The reason for the different profiles is due to the heat that builds up when a gun is fired full-auto.  If you take a light barrel and shoot 5 shot groups rapidly on different targets you'll note that the groups will be about the same size, but each group will have a slightly different point of impact.  This is no big deal in combat, as you're shooting a man, not a small bullseye. That's not to say that a lightweight barrel is bad.  There's nothing wrong with one of them, but they heat up more rapidly.  What might be interesting is a heavy barrel profiile that's fluted.  As far as I know no one makes one, but it would be interesting to see.

That is only a select run of A1s, most only have a full auto trigger group.

Quoted:The reason for the different profiles is due to the heat that builds up when a gun is fired full-auto.  If you take a light barrel and shoot 5 shot groups rapidly on different targets you'll note that the groups will be about the same size, but each group will have a slightly different point of impact.  This is no big deal in combat, as you're shooting a man, not a small bullseye.

Free float the light barrel and the problem goes away completely.

I have seen a bushy heavy 16 incher with fluted barrel

it was fluted under the hand guards and in front of them as well.

it is a very good looking and functional rifle, the only problem was it is a post ban with the mini y compensator on it--man those things are loud.

Quoted: M4 barrels are light under the handguards and the selector switch on an M4 is safe-semi-burst. M4A1 barrels are heavy under the handguards and the selector switch on an M4A1 is safe-semi-auto.

Up to 1999, the M4A1s all had the regular barrel and were still being produced with the regular barrel up to 2003.

I'm a bit confused about STLRN's comment, since it sounds to me like he corrected me for saying the same thing that he did.

As for my knowledge of M4A1 barrels, I got out of SF in late 1992 due to a HALO accident.  In 1997 or 1998 I visited the team that I had been on when I got hurt and took a look at their equipment.  The M4A1 that I took a look at at that time had a heavy barrel under the handguards.  I visited the weapons branch summer before last and they had full heavy barrels then as well.  That's my only 1st hands experience with an M4A1.  I was just passing along information that I had seen 1st hand.  

i like the light profile

Quoted:  If  the weight is at all a concern,  I think a 14 1/2"  SOCOM barrel weighs just as much as a 16" lightweight M4 barrel.  If you don't mind sacraficing 1 1/2"  of barrel and getting a flash hider perm pinned.

A 14.5" standard, light under the handguards barrel may weigh the same as a 16" lightweight, but not the SOCOM.

I could care less either way.

We are looking at the difference of what? Maybe a pound.

That pound will not make me prefer one profile over the other.

Show me which one has the lowest price and I am more liely to but that one.

If you think that that one pound will mean the differenece on whether you fail or succeed, you need to go to the gym.

Hi guys,
    I just took some pics of some different 10"-16" barrel profiles for reference. The 16" fluted Bushy HB will shoot 0.9" @ 100 5 shot using 69gr. Sierra HP. Fluting the Bushy HB reduced wt. by only .5 lb, but it improved the "pointability" of the upper by making it very neutral in wt. distribution. The 16" fluted Bushy is the most accurate carbine length upper I have. All these bbls are chromed 1x7 except the Bushy is chromed 1x9.
                                                                      HTH,
                                                                       Carey
16" fluted Bushy HB w/AK break
16" Colt M4
14.5" Colt SOCOM
14.5" Colt pencil
11.5" Colt LWt.
10" Colt LWT.

Very Nice!

thanks for the pic.

could we get one of the fluted bushy together on its lower?

Quoted: I'm a bit confused about STLRN's comment, since it sounds to me like he corrected me for saying the same thing that he did. As for my knowledge of M4A1 barrels, I got out of SF in late 1992 due to a HALO accident.  In 1997 or 1998 I visited the team that I had been on when I got hurt and took a look at their equipment.  The M4A1 that I took a look at at that time had a heavy barrel under the handguards.  I visited the weapons branch summer before last and they had full heavy barrels then as well.  That's my only 1st hands experience with an M4A1.  I was just passing along information that I had seen 1st hand.

Not all M4A1s in Group have the heavy bbl.  The heavy bbl was designed and added to prevent cookoffs with the weapons as ODAs/Rangers shoot allot.  Other methods were tried and tested as heat sinks, flueting etc.  I still prefer the orginal bbl profile on my M4A1 over the heavier bbl.  Weight does added up when you add the rail system, optics, IR laser, flashlight, VFG etc.  Have seen some marked M4 and M16A2 carbines with full auto instead of burst but not standard (still US property).  

CD

O,
    Here you go.  
                                                                Carey

And it's bigger brother. This one shoots 69 gr Sierra HPs under 0.3 MOA. I do beaver control in Mississippi with it. The bore is not chromed, so it requires more care when out in the weather.

thanks

very nice

Quoted: Not all M4A1s in Group have the heavy bbl.  The heavy bbl was designed and added to prevent cookoffs with the weapons as ODAs/Rangers shoot allot.  Other methods were tried and tested as heat sinks, flueting etc.  I still prefer the orginal bbl profile on my M4A1 over the heavier bbl.  Weight does added up when you add the rail system, optics, IR laser, flashlight, VFG etc.  Have seen some marked M4 and M16A2 carbines with full auto instead of burst but not standard (still US property).   CD

C-Diver-

The "original bbl. profile" you refer to is the intermediate ?

In between a Heavy and a Lightweight?

TIA

Go look at the Black Rifle II book on pages 94 and 95.  What is stated in that book is that the M4 barrels were originally made thinner under the handguards.  However, SOCOM troops have an odd way of exfiltrating an area under fire.  Rather than use the old Vietnam CQB trick of a team exfiltrates in line with the last man in line emptying one mag, then throws a grenade and then peels off and goes to the head of the line, then the man who was next to last in line is now the last man in line so he empties one mag, throws one grenade, and then he peels off and goes to the head of the line, then the man who was next to the last man is now the last man and he does the same,  So, what you are doing is leaving an area while the enemey receives a full mag of full auto fire followed by a grenade, then a full mag of full auto followed by a grenade.  This provides a gradual exiting form the area but keeps your enemy pinned down.  With this type of shooting you empty a mag and your gun has a cool down period before you work your way back to the end of the line and you shoot it again.  Well the new SOCOM method is for everyone to stand on line or behind cover and empty mag after mag after mag with no rest in between magazines.  Their theory is that they saturate the area where the enemy are suspected of being with a very high concentration of bullets.  The problem was that a barrel could achieve its "tranformation" temperature which is around 1100 degrees F to 1,375 degrees F.    This was done by firing 540 to 596 rounds, which had to be fired within 3 to 3 1/2 minutes.  That was the equivalent of shooting 18 to 19 of the 30 round mags within 3 1/2 minutes.  That is a lot of rounds and that is a lot of heat.  This especially occurred in Afghanistan, where temps were around 100 degrees to 110 degrees F and this added to the heat buildup.  By making the new barrels thick under the handguards, they can now withstand that amount of full auto fire without blowing a barrel.  So, the thicker M4 barrels are referred to as the SOCOM M4 Barrels.  I shoot full auto, but I let my weapon rest after one magazine.  At worst, I might shoot two mags in a row.  This is not sustained full auto fire, but bursts.  Most people find that full auto is good to suppress the enemies fire until you can break out of an ambush.  For example, the ememy springs the classic "L" shaped ambush on you.  Everyone switches to full auto and charges the right angle of the "L" and so much lead is flying at the bad guys that they keep their heads down.  But then you are back to the accurate single fire that is the most useful.  I doubt any of us will abuse our M4 barrels like the SOCOM troops are doing.  So, the slim barrel under the handguards M4 barrels should be fine for full auto and single shot, just not for almost 20 magazines of 30 rounds as fast as you can slap them in.  Now for those who want the ultimate SHTF weapon, and want to pay the extra bucks, buy one and be the first boy on your block to be able to run that amount of ammo through your rifle without blowing it up.  If I could trade my current skinny M4 barrels for SOCOM barrels, I would take them.  But if I have to pay money for them, I would not do it.  

Charles Tatum
Alamo Professional Arms

You in no way want or need the heavier barrel.  I have used my M4 "thin" profile barrels for full and semi auto use and never wished I had the pig of a mistake HBAR I sold that was my first AR.  If you gave me a free HBAR I would sell it.