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11/22/2017 10:05:29 PM
Posted: 7/28/2004 8:44:27 AM EST
From the Autoweapons.com listing:


COLT M4A3 H/B UPPER ASSY - NEW IN FACTORY WRAP - THESE ARE THE VERY RARE AND NEVER AVAILABLE TO THE PUBLIC COLT M4 HEAVY BBL....THESE ARE THE ONES IN CURRENT USE WITH SOCOM FORCES IN THE MIDDLE EAST -- NOT THE STANDARD M4A3 BUT HEAVY BBL UNDER THE HANDGUARDS, REQUIRING A SPECIAL HEAVY BUFFER "2" TO PREVENT "BOLT BOUNCE".....THE UPPERS HAVE THE WHITE R.A.S. NUMBERS -- COMPLETE W/ CARRY HANDLE





What is the story on this profile? Why did SOCOM feel that the heavy barrel was needed under the handguards? And, most importantly, can I find such a profile for less than $1795?

Link Posted: 7/28/2004 8:50:09 AM EST
To maintain barrel integrity under sustained full auto fire,
Link Posted: 7/28/2004 8:54:59 AM EST


the story is that the original M4 barrel was a terrible design.

the area where both heat and moment are [just about] greatest is where the M4 has the smallest cross-section and profile. bad idea.

many will argue that there haven't really been any failures or anything like that, but that doesn't mean there isn't room for improvement.



Link Posted: 7/28/2004 8:58:21 AM EST


M4A1 BTW
Link Posted: 7/28/2004 11:04:59 AM EST
SAW Sales has them for under $1K...

-Cap'n
Link Posted: 7/28/2004 11:19:56 AM EST
OR, you could just get a HBAR, and not be worried with such problems.
Link Posted: 7/28/2004 11:21:13 AM EST
SF wanted more meat under the HGs to handle the heat of extended full-auto fire since they don't usually have a M249 along for that. I've never heard of any special designation for M4s with this barrel, and never anything except M4 (burst) and M4A1 (auto). What's an M4A3?


NOT THE STANDARD M4A3 BUT HEAVY BBL UNDER THE HANDGUARDS, REQUIRING A SPECIAL HEAVY BUFFER "2" TO PREVENT "BOLT BOUNCE"

Why would the barrel thickness have anything to do with bolt bounce? And how could an AR have bolt bounce anyway?
Link Posted: 7/28/2004 11:30:50 AM EST
[Last Edit: 7/28/2004 11:31:10 AM EST by Feedingcannibal]

Originally Posted By Mike_L:

Why would the barrel thickness have anything to do with bolt bounce? And how could an AR have bolt bounce anyway?



I was wondering the same thing.



SAW Sales has them for under $1K...

-Cap'n



I looked at Saw's site (sawlesales.com) and I believe you are correct. What's with the huge price difference?

Although I'm not a full-auto guy, I like the idea of this profile, if only for its uniqueness and, I would assume, some benefit of durability.
Link Posted: 7/28/2004 11:40:56 AM EST
He just quoted the ad, which says "special heavy buffer '2' " to prevent bolt bounce..... I think they are saying with a full auto weapon. Bolt bounce not an issue with a semi auto AR, but it is with shorter barreled M16/M4 variants.
Link Posted: 7/28/2004 11:57:28 AM EST
I can understand changing buffer weight to affect cycle-speed, but I don't see how "bolt-bounce" could be an issue with any AR. And certainly not how barrel weight would matter. (Barrel length yes, weight no.)
Link Posted: 7/28/2004 12:13:17 PM EST

Originally Posted By Feedingcannibal:

<zap>

And, most importantly, can I find such a profile for less than $1795?




I have a RRA heavy profile, M-4 chromelined 16" pre-ban barrel in 1x9 twist. Came from Pete-in-NH for $200. Looks just like that.

I know it's not Colt, just thought I'd toss that idea at ya.

Danny



Link Posted: 7/28/2004 1:19:15 PM EST
SAW

Part #: SA02019
Description: BARREL & FRONT SIGHT ASSY LE6921HB/R0921HB, 1/7 M4HB- 14.5in CHROME LINED
Price: 495.00




Link Posted: 7/28/2004 2:05:08 PM EST

M4A1 Barrel


SOCOM M4 Barrel

Note that the SOCOM barrel is even heavier than the M4A1 barrel and that it has no turned-down section under the handguards.

Also, the LE6921HB is not the same as the SOCOM barrel. I've seen the SOCOM barrels (without upper) for sale for $850. As high as S.A.W.'s prices are, I know that they aren't offering the same barrel for $350 less.
Link Posted: 7/28/2004 2:15:50 PM EST
M4Madness,

If you looked at my photo you will see the top is a RO921(M4A1HB) or "SOCOM" bbl - the lower one is the standard M4A1 barrel.

The "SOCOM" barrel does in fact have flat cuts on the barrel so the M203 can mount.

Wait I will take a better pic.
Link Posted: 7/28/2004 2:26:57 PM EST
Link Posted: 7/28/2004 2:42:42 PM EST
[Last Edit: 7/28/2004 2:43:44 PM EST by KevinB]
It is a barrel - nothing special about it... The only reason crazy prices where abounding is cause Colts production was not going to civvies - now they seem to have spares.















Link Posted: 7/28/2004 2:44:53 PM EST
SO ENDETH THE LESSON


Link Posted: 7/28/2004 2:55:07 PM EST

Originally Posted By M4Madness:
photos.ar15.com/ImageGallery/Attachments/DownloadAttach.asp?iImageUnq=3088
M4A1 Barrel

www.autoweapons.com/photosv/coltm4a3hbuppa.jpg
SOCOM M4 Barrel

Note that the SOCOM barrel is even heavier than the M4A1 barrel and that it has no turned-down section under the handguards.

Also, the LE6921HB is not the same as the SOCOM barrel. I've seen the SOCOM barrels (without upper) for sale for $850. As high as S.A.W.'s prices are, I know that they aren't offering the same barrel for $350 less.



The R0921HB/LE6921HB barrel is indeed the M4A1HB "SOCOM" barrels. I've owned 2 so far, they're the exact same thing. The story I heard about them was that Colt accidentally sold 10 or so off as R0921 barrels, and that these few magic ones were the only in civilian possession. Now they're fairly commonplace, as most any Colt dealer can get them.

They're a good investment for one who plans on mounting an M203, and suppressing the weapon while firing obscene amounts of ammunition in a short order of time. Other than that... Well, I'll leave that up to the other folks that have them.

SAW is offering them at that price because that's Colt's retail price, just like everything else they list.

-Cap'n
Link Posted: 7/29/2004 3:15:02 AM EST
[Last Edit: 7/29/2004 3:16:22 AM EST by Feedingcannibal]

Originally Posted By Capn_Crunch:

They're a good investment for one who plans on mounting an M203, and suppressing the weapon while firing obscene amounts of ammunition in a short order of time. Other than that... Well, I'll leave that up to the other folks that have them.

-Cap'n




Appreciate all the good info. I know the above statement by Capn_Crunch is true, and that I will never (barring massive social upheaval) have either an M203 or full auto, but...

I want one just the same.



Oh, and KevinB, I'm not seeing your pictures, which I am very interested in.
Link Posted: 7/29/2004 6:42:58 AM EST
I think the ARF photo server is having a fit.
Link Posted: 7/29/2004 10:57:04 AM EST
Here is a pic of my Colt SOCOM barrel:

Link Posted: 7/29/2004 11:25:18 AM EST
Link Posted: 7/29/2004 11:42:03 AM EST

Originally Posted By Hawkeye:
These will obviously have M4 feed ramps, right?



That is correct.
Link Posted: 7/29/2004 12:47:38 PM EST
[Last Edit: 7/29/2004 12:50:47 PM EST by M4Madness]

Originally Posted By KevinB:
M4Madness,

If you looked at my photo you will see the top is a RO921(M4A1HB) or "SOCOM" bbl - the lower one is the standard M4A1 barrel.

The "SOCOM" barrel does in fact have flat cuts on the barrel so the M203 can mount.



My bad. I stand corrected.

Anyway, I've got a suppressed M4 upper (LE6921) for my registered M16. I wonder if I'd ever need something like the SOCOM barrel.
Link Posted: 7/29/2004 12:52:50 PM EST
M4Madness - no harm.

IMHO Cap't Crunch is 100% - there is no need for the HB. You are abusing the weapon if it is causing damage to the 'normal' M4 barrels. 3+ mag dumps back to back (f/a with a suppressor) is not trainign - no matter how to slice it.
Link Posted: 7/29/2004 2:28:51 PM EST
I sent my 16" HBAR to KKF to get turned down forward of the FSB. Cheaper than $1795.00 !!!!!

Link Posted: 7/29/2004 3:25:01 PM EST
Thanks for those pics of the M203 with the barrel KevinB.

I always wondered how they mated together.

Link Posted: 7/29/2004 5:51:18 PM EST

Originally Posted By dmk0210:
Thanks for those pics of the M203 with the barrel KevinB.

I always wondered how they mated together.




The gap is where it would fit on to the barrel nut.
Link Posted: 7/29/2004 6:05:07 PM EST
What do they measure under the handguards

I heard Diemaco makes a heavy M4 barrel that measures .750 under the handguards.
Link Posted: 7/29/2004 6:18:03 PM EST
Link Posted: 7/30/2004 8:28:28 PM EST

Originally Posted By dmk0210:
Thanks for those pics of the M203 with the barrel KevinB.

I always wondered how they mated together.




+1

Link Posted: 7/30/2004 8:47:59 PM EST
Bolt bounce is an issue on full auto or burst w the M-4 heavy barrel w/out the proper buffer installed. Seen it happen quite a bit.
Buyer beware, if you buy a heavy barrel the Army dumped the original heavy barrel because of Colts crappy Q.C. and went to a different barrel. If the Barrel is made before MAR 02 it is the older H.B. design and subject to a 10-15% (in my experience) failure rate for repeated failures to extract-and that is with the black spring and "O"Ring installed in any mode of fire (S/A, F/A, Burst) and it starts to happen worse after about 30-60 rounds fired. This one requires the "H" buffer. So be careful.

The Newer H.B. design after MAR 02 (Stamped on the front of the larger contour of the barrel, behind the forward handguard plate)has a different finish on the chamber walls (tighter Micro-inch surface spec.). It has less extraction resistance which stacks up in faster bolt cycling increasing the possibility for the bolt carrier rebound (aka: "bolt bounce") it operates on the tight end normally for the forward stroke movement of the bolt for cartridge pickup and bolt carrier rebound, not much margin for bad mags here. The "H-2" buffer is required for F/A and burst, rebound does happen occaisonally in semi-auto but not very often at all. If it comes with a bolt make sure the bolt has a "gold" spring.
Link Posted: 7/30/2004 9:26:48 PM EST
You paid? How much!!!
Link Posted: 7/31/2004 12:26:21 AM EST

Originally Posted By M1-Matt:

Originally Posted By dmk0210:
Thanks for those pics of the M203 with the barrel KevinB.

I always wondered how they mated together.




+1



+1

MN
Link Posted: 7/31/2004 6:48:15 AM EST
Actually, that gap in the HB on an M4A1 is to allow you to mount IR aiming lasers (assuming you aren't using a rail system) The cut out on the front part of the barrel (forward of the front sight assembly) is for the M-203.

Of course the possability exists that you were talking about the notch forward of the front sight, in which case... my bad, I wasn't paying attention.
Link Posted: 8/1/2004 12:48:18 AM EST
The cutouts on the side of barrel (under the handguards) are for clearance to get the M203 on the barrel and the machined smaller diameter up front is for the forward mount for the M203 (Either a semi-permenant mounting or the Q.D. mount).
Link Posted: 8/1/2004 12:41:05 PM EST

Originally Posted By KMFDM:
Bolt bounce is an issue on full auto or burst w the M-4 heavy barrel w/out the proper buffer installed. Seen it happen quite a bit.
Buyer beware, if you buy a heavy barrel the Army dumped the original heavy barrel because of Colts crappy Q.C. and went to a different barrel. If the Barrel is made before MAR 02 it is the older H.B. design and subject to a 10-15% (in my experience) failure rate for repeated failures to extract-and that is with the black spring and "O"Ring installed in any mode of fire (S/A, F/A, Burst) and it starts to happen worse after about 30-60 rounds fired. This one requires the "H" buffer. So be careful.

The Newer H.B. design after MAR 02 (Stamped on the front of the larger contour of the barrel, behind the forward handguard plate)has a different finish on the chamber walls (tighter Micro-inch surface spec.). It has less extraction resistance which stacks up in faster bolt cycling increasing the possibility for the bolt carrier rebound (aka: "bolt bounce") it operates on the tight end normally for the forward stroke movement of the bolt for cartridge pickup and bolt carrier rebound, not much margin for bad mags here. The "H-2" buffer is required for F/A and burst, rebound does happen occaisonally in semi-auto but not very often at all. If it comes with a bolt make sure the bolt has a "gold" spring.



KMFDM,

Thanks for the good info you gave. My Colt SOCOM HB is dated 01/01, but I have not had any problems like you mentioned and I have ran several thousand rounds through mine, mostly in F/A. However, I use a Colt bolt with the SAW heavy duty extractor spring as well as the DPMS two piece buffer (which is actually heavier than a full length buffer) and that may be why I haven't had any problems. I have never tried mine with a standard extractor spring or buffer.
Link Posted: 8/2/2004 5:43:54 AM EST
KMFDM,
So the "bolt bounce" is at the back of the cycle, bouncing off the buffer tube?
Link Posted: 8/2/2004 6:29:47 AM EST

Originally Posted By Mike_L:
KMFDM,
So the "bolt bounce" is at the back of the cycle, bouncing off the buffer tube?



No, the carrier bounces upon closing.
Link Posted: 8/2/2004 6:33:53 AM EST

Originally Posted By Hotgun:

Originally Posted By Mike_L:
KMFDM,
So the "bolt bounce" is at the back of the cycle, bouncing off the buffer tube?



No, the carrier bounces upon closing.


I just can't picture how that's possible.
Link Posted: 8/3/2004 12:45:09 AM EST
Its kind of like holding a hammer in your hand lightlyand let it strike a hard object like a block of steel.It will bounce off of it.When the bolt carrier hits the barrel it bounces back slightly.This usually not a problem on semi because the recoil spring pushes the bolt carrier back forward before you have time to pull the trigger.On auto the hammer is released when the carrier hits the barrel.It bounces back before hammer falls completely.SJR556.
Link Posted: 8/3/2004 6:41:16 AM EST
I thought only the bolt touched the barrel, not the carrier. And that the action of the bolt seating into the carrier would cushion that.
Link Posted: 8/3/2004 7:23:27 PM EST
[Last Edit: 8/3/2004 7:25:14 PM EST by KMFDM]
The bolt carrier rests on the barrel extension in battery, it happens on the forward stroke of the carrier when it impacts the extension and bounces back a little. Not enough to fully unlock the bolt but enough for it to retard the forward motion of the hammer and give a light strike to the primer. The buffer acts as a "dead blow" hammer and is supposed to stop it from happening. If a higher cyclic rate is obtained it changes things around quite a bit.

CA-AR-M16, You probably got a good barrel so that saves you alot of grief.
Link Posted: 8/18/2004 12:04:08 AM EST
Link Posted: 8/18/2004 12:14:57 AM EST
Frozenball - sorry the PAQ barrel mount with not work on the HB M4's. It is a cut flat not a .650 circle. KMFDM and I are correct (see pics)

I took my RAS off my C8 SFW - the barrel look like .820 or something - I had thought .750 but it lloks thicker than forward of the FSGB. If I get time I will venture over to our armourers I wil ask them to mic it.
Link Posted: 8/18/2004 2:32:49 PM EST
I thought KKF was going to be able to machine these from standard Colt barrels such as the 16" HBAR (Yes I know it would be 1/9 but what the heck)
Link Posted: 8/18/2004 5:30:20 PM EST

Originally Posted By Troy:

Originally Posted By KevinB:
IMHO Cap't Crunch is 100% - there is no need for the HB. You are abusing the weapon if it is causing damage to the 'normal' M4 barrels. 3+ mag dumps back to back (f/a with a suppressor) is not trainign - no matter how to slice it.



Agree 100%, and for those without full-auto, that goes double. You're just carrying extra, useless weight, and you'd get virtually the same thing with a $200 Bushmaster HBAR barrel (heck, you can pay to have one turned down exactly like this Colt barrel and STILL pay half as much - but, again, why?).

-Troy



Here are some of the reasons I'm considering investing in one of these SOCOM Colt HB uppers:

1. Durability.

In a lone wolf/SHTF scenario, one might be required to lay down alot of fire, even in semi-auto, depending upon the circumstances at hand. In addition, perhaps the heavier barrel could be more advantagous if one had to rely soley upon it for extended periods of time with no backup or material support.

2. The uniquness of the barrel would make a nice addition.

3. LCF

4. The SOCOM upper is actually cheaper than the standard M4 at Sawlesales (by $5 or so).

Now, I realize that the latter three reasons could be considered somewhat trivial, but they are considerations for quite a few of us.

I'd be interested in any input. The new Colt SCAR submission sounds amazing, but it could be a long damn time before they are available commercially, if at all. So I'm leaning towards a Colt M4 or this Colt SOCOM upper.
Link Posted: 8/18/2004 7:28:30 PM EST
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