Looking at getting a new upper for one of the carbeans (I prefer Colt - I drink the Kool Aid)

Was thinking just the standard 14.5-inch M4 (6921) barrel, but seem to be seeing a lot of the heavier M4 SOCOM barrels out there too and had a couple questions...

What (if any) advantage is there with the heavier SOCOM barrel?

What is the difference in weight between the two barrels (I'd be building up the upper the same either way, so the only real difference is going to be the barrel).

Thanks.

4oz is the weight difference. As for which is better, look up Colt's full auto test comparing the two barrels.

Topic Moved

As the poser above said, the weight difference is only 4oz, which I find negligible. Also, the weight of the barrel is closer to the center of mass of the weapon, so it handles better than the govt profile which puts additional weight out at the muzzle. Were it me and I could find a SOCOM at a reasonable price, that's what I would do.

As others have said - the weight difference is four ounces.  

The RO921HB profile barrel (M4A1 SOCOM) has several advantages to offset the weight difference, however they're not necessarily critical for everyone, so it's kind of up to you whether you want the weight penalty.  At the end of the day, they're both good, quality barrels, but they have the limitation of being military production grade chrome lined barrels.  

The original onus behind the M4A1 HB profile barrel was because the "wasp waisted" government profile M4A1 barrles (RO921/920/977/6921/ect.) were bursting under heavy automatic fire (talking several continuous mag dumps during SOF break contact drills - think the end of Tears of the Sun - but y'know... more professional military and less Hollywood).  

Part of the problem was simply the thinness of the barrel, but another part was because of the somewhat "odd" nature of the government profile barrel (thick in front - thin in the back) the uneven heat distribution was causing catastrophic failure.  The point of failure tended to be right behind the handguard cap where the thin part of the barrel "flares" into the .750 FSB journal.  

The solution was, therefore, to make the barrel thicker throughout and create a medium contour barrel (despite Colt's "HB" designation) that gradually flares toward the barrel extension, and eliminate the uneven heat distribution.  Furthermore, making the barrel thicker resulted in the barrel taking longer to heat up to a critical level.

Additional benefits that came from the thickening of the barrel was the fact that the RO921HB profile is hypothetically more accurate (more precise, actually, but that's neither here nor there) than a comparable RO920 barrel not only because it resists heat better, but the thickening of the barrel makes it stiffer for its length than the RO920 barrel.  Again, keep in mind that these are still military production chrome lined carbon steel barrels - so they're not exactly designed for precision and accuracy, but all other things being equal, a stiffer barrel will be more accurate.  

Another side benefit is for suppressed use - 14.5" barrels, while very short compared to a 20" rifle are still pretty long tubes.  When hanging a heavy suppressor on the end of the barrel, there's is POI shift to contend with, the suppressor changes the harmonics, as well as being a heavy weight at the end of a long lever - and consequently, as the barrel heats up, it will exhibit more droop compared to a barrel without a suppressor.  As with the accuracy benefits - the stiffer the barrel, the more it will mitigate these problems.  It won't eliminate them, but it will help.  

As a counter to these benefits, however - during testing, it was found that the change in the barrel harmonics of the RO921HB barrel increased the potential for bolt bounce, necessitating H2 weight buffers as opposed to the H that was being used in the original RO921.  While bolt bounce is a problem most often associated with automatic fire, it's still not something you want in a semi-auto system either.  I tend to feel that an H2 buffer should be a companion to the RO921HB barrel and used together.  

As far as personal use goes - I've long since used the RO920 and government profile barrels.  Back before my suppressor days, I was so used to the government profile weight and balance, when I picked up an RO921HB barrel, I found the extra weight to be irritating - I knew about the heat and accuracy benefits, but for me, they were less important than maintaining the balance and weight I was used to.  The difference is in fact not that severe, but I was pretty intimate with my RO920s, snuggling with them in the mountains and what have you.  

Fast forward a couple years, now I do about 50% of my shooting suppressed and have gotten used to switching from suppressed to unsuppressed weapons - relative to the weight and balance change between a suppressed and unsuppressed 14.5" barrel, I barely notice four ounces any more.  Also, for me, the biggest benefit for my type of shooting is the advantages that the RO921HB profile barrel has for suppressed shooting - mitigating droop and POI shift.  The other benefits are "bonuses" and I'm in the process of slowly replacing most of my government profile barrels with M4A1 HB barrels.  

Probably more than you were looking for, but hope it helps.

~Augee

I've used one and they make the M4 front heavy. That 4oz is noticeable when carrying all day or doing shooting drills. No advantage on a semi only weapon.

Thanks Augee for the very interesting post!  Particularly the part about bolt bounce in the SOCOM barrel.  I've heard that an H2 buffer is recommended for the SOCOM barrel, but didn't realize that this was the reason for that.

So who has the best price on a Colt 14.5 inch socom upper?

Thanks guys for all the input, I really appreciate it.


That, and who has the best prices on the RO920 barreled uppers?

+1   Seen the barrel just not the rifles or uppers.

I know Specialized Armament carries complete Colt uppers.  But be prepared to pay over 1000 dollars for it.

I know Ken and know he's got em... like you said, they're going to be expensive. He does GREAT work and for some things I'd want no one else and never blink an eye at the price, but I imagine I can find what I need (looking for box stock here) without paying the SAW prices.

eta: what better place to learn to love the Kool Aid?

I'm not sure I understand why someone would buy an upper for 1000 dollars from Specialized Armament when a complete Colt rifle is 1,150 from a gun store....
Also, you can buy a complete Colt upper from Colt for 685  http://www.coltsmfg.com/ShopOnline/tabid/62/ProdID/301/CatID/35/Default.aspx

not the Socom barrel...

Yes, but just an example of what a complete upper should cost.  Not 1000 dollars.
I will call the Colt CS department today and see if they can get the Colt socom complete upper in 14.5.
Also, Operation Parts may be a good source for Colt.

Didn't see any on here



Nor on Operation Parts either....

Reply to Rick_A;



OP is looking for a 14.5" barrel. Comparing the advantage of a heavy barrel for semi-auto use to a long heavy barrel varmit gun is apples and oranges. On a semi-auto 14.5" barrel, the heavy barrel will not have a noticeable advantage Kinda like saying, everytime you bend your elbow you create wear on your shirt sleeve. It's true but the wear is so negligable it's not measurable.

And definitely not enough to just the additional cost of the SOCOM barrel over a regular M4 barrel. I used one in 2006 and it sucked. The extra weight was very noticeable yet provided no advantage. Military use is for sustained FA fire which is questionable as FA fire is not used much except for break contact drills.

I have a 14.5" SOCOM profile barrel on my AR. I chose it because I snagged it used cheap, and for the price it's great. That said, it is stupid heavy. I'd prefer the gov profile to the SOCOM, and I'd prefer a lightweight to both of them. I do not have an auto lower, and I'm not mounting an M203 on it anytime soon.

TC - I agree with you for the most part - but again, the primary attraction of the 921HB barrel for me in civilian use is the fact that it's a superior profile for use with a suppressor.  

While the 4oz. is definitely noticeable - it's nothing compared to sticking a can on the end.

I'd say unless you were planning to do a significant amount of shooting either on FA or suppressed, the 921HB profile would be desireable.  

On an unsuppressed semi, I generally agree with you.

~Augee