Someone who knows something about M4 barrels, tell me this:

What is the purpose of an M4 barrell versus a regular C.A.R. barrel? What is the purpose of
the skinnier part of the barrel? Is the M4 barrel lighter than a regular CAR barrel? Is the skinnier part of the barrel for a bi-pod attachment or something? Also, I was wondering if the skinnier part of the barrel is weaker... Any reported problems with the M4 barrel design. I'm about to order an M4 kit, and before I do, I just wanted to know.

Grenade launcher mount

ed to say plenty thick.

Go ahead and order your M4 barrel unless you want to order an ultra light barrel instead.

To look cool.


In a Bushmaster 16" length, the M4 barrel weight 1.6 ounces less than a HBAR fluted barrel. That's why I ordered the fluted barrel from Bushmaster on my new upper. HBAR accuracy,durability and the fluted barrel looks WAY cooler than the stupid M4 !

Basically, the HBAR fluted can take WAY MORE HEAT than an M4 can. If fired on full auto for more than 200 rounds or so, there have been incidents where the barrel began to droop & a round went THRU the barrel. Someone had posted pics of such a failure on this site 2 years ago.

Nope, I'll take a fluted HBAR over a M4 any day.

You won't have any problems with the cutout section on the M4 barrel. Like others have said, it's for mounting a grenade launcher - but for 99% of us out there, it's just for looks.

You'll never have any problems with an M4 barrel. it may get hot, but you will know if you're going to destroy it, because in semi thats probably 500 rounds fired as quickly as you can shoot and reload. Its slightly stronger than a CAR lightweight barrel, and certainly more than 1.6 ounces lighter than an HBAR.

So what you are saying is all the M4's our military is using would melt to that point after 200 rounds? How do you explain the hours long firefights in Iraq (circa2003) where thousands of rounds were fired through M4's without such failures? Sounds like bad non mil-spec barrels to me.

This is all hearsay and anecdotal, but I also heard the military was having problems melting the barrels on their M-4s during sustained full-auto fire, and the weak spot was always the M203 cuttout.  I never heard it was at 200 rounds.  I'm not an expert by any means but I'd guess it was way more rounds than that.  I'm not certain, but I think I heard this from the folks at Wilson Combat.  

That said, I bought my Colt LEO rifle (early this year) with an M-4 barrel simply because it looks bitchin' h
I shot about 300 rounds through mine almost as fast as you could pull the trigger and there were no ill affects.  On the other hand, a guy who is known in CA bay area LEO circles as a kind of "AR god" (he worked for many years for the DOD weapons division testing cool stuff), said the fluted barrel is the best one to get on your AR.

I was a big M4 barrel fan but have since "seen the light" and converted to Bushy Ultralight barrels that shoot every bit as well and handle like a dream.

Just to add, the weakness of an M-4 barrel only shows itself under suppressed auto fire.  The M-203 cut out gets too hot and the rifling begins to melt.  When an M4 and an M16A2 barrel were tested to destruction, the M4 barrel lasted longer, and the gas tube lasted longer still.

Seth (borrowing account)

Has anybody mentioned that it looks bad ass!!hug.gif

The thin sections of the barrel are like a weak link in a chain, that's where failures occure. The spec-ops are getting away from hacked up heat sink sectioned barrels for launchers, and going back to heavy barrels that are free floated, and so is the launcher, off the rail, not the barrel.
Jack

Quoted: So what you are saying is all the M4's our military is using would melt to that point after 200 rounds? How do you explain the hours long firefights in Iraq (circa2003) where thousands of rounds were fired through M4's without such failures?hr

Do a search on this board.  In the past month or so someone posted a link to a .pdf file which was taken straight from one or another Army test lab.  The M4 barrels lasted for about 550 rounds when fired in full auto, without any cool down period besides the mag changes.  

This was done because of complaints, I am told, by the specops community who wasn't happy about their carbines not being employable as light machine guns.


hisMarine Corps Gazette), but it really does not make a good light machine gun.  This is due to its closed bolt system, substantial difficulties making a reliable open bolt version (or so at least I've been told), and a general inability to take the stress of this kind of sustained full auto fire.

Heavy barreled assault rifles have generally made for poor or at least very limited light machine guns (ref: various FAL variants, the HK's - though I hope that HK has done better with the MG36).   This is probably even more the case with the M16, which was primarily designed to be a 6 pound carbine and not a modular carbine-rifle-LMG system (e.g. the Stoner 63, or - one would hope - the G36 again).  

The biggest problem with the M16 LMG was supposedly the aluminum upper.  One made of steel may have solved the problem.

Seth

Combat Jack that definitely could be, but would you really feel comfortable shooting 1000 straight rounds of belt fed ammo through anything like the standard M16 bolt?   Me thinks a Shrike-type upper would have been a better idea (assuming that the design's technically feasible).

Ah, but we digress from the topic of the thread.................

All of this is darn interesting. I ordered a kit with an M4 barrel, chrome-lined. Does the chrome-lining help when the barrel is heated up? I can't see myself ever shooting the rifle for 500+ rounds superfast...auto, because it is a semi-auto gun. But, let's say, I shoot 6 or 700 hundred rounds in a short period of time? You guys here on the forum....what's the most you've shot out of your M4 barrels in, say, one trip to the range?

Final couple of questions:

Has anyone here ever had an M4 barrel fail on them?

And, I could still call the company I just ordered the M4 barrel from (they haven't shipped yet) and change my order...to, say, a flutted barrel or something. I love the way the M4 looks. Should I change my order, or just stick with the M4 I originally wanted? What do you guys think?

Quoted: Combat Jack that definitely could be, but would you really feel comfortable shooting 1000 straight rounds of belt fed ammo through anything like the standard M16 bolt?   Me thinks a Shrike-type upper would have been a better idea (assuming that the design's technically feasible). Ah, but we digress from the topic of the thread.................

I wouldn't feel comfortable firing 1000 rounds straight thorugh any belt fed gun, if I owned it (with a 6 barreled gat possibly being the exception).

I've done at least 300 rounds during one session in semi using my Bushmaster super lightweight barrel with no ill effects.  That was over a period of maybe an hour or so.  The super lightweight barrel is even slimmer than the M4 barrel, so you should be good to go.  Just get something that's made with chrome-lined 4150 steel.  Colt, LMT, CMMG, and Bushmaster all have offerings that fit this bill.

Quoted: All of this is darn interesting. I ordered a kit with an M4 barrel, chrome-lined. Does the chrome-lining help when the barrel is heated up? I can't see myself ever shooting the rifle for 500+ rounds superfast...auto, because it is a semi-auto gun. But, let's say, I shoot 6 or 700 hundred rounds in a short period of time? You guys here on the forum....what's the most you've shot out of your M4 barrels in, say, one trip to the range? Final couple of questions: Has anyone here ever had an M4 barrel fail on them? And, I could still call the company I just ordered the M4 barrel from (they haven't shipped yet) and change my order...to, say, a flutted barrel or something. I love the way the M4 looks. Should I change my order, or just stick with the M4 I originally wanted? What do you guys think?

I've done four mags in three minutes on a stock M4 without issue. Just don't touch anything metal. I've put 500 rounds through one rifle in a few hours without issue.

Chrome lining makes the biggest difference when the barrel is hot. A really shot barrel will generally never group again, unless its chrome lined. Still not undamaged, but better off.

Thanks, guys. I think I'm stickin' with the M4 then. It sounds like you have done some serious shootin' with them without issue. And yes, I am getting the chrome-lined barrel.

There was a report a while back by SOCOM about the problems they were having with M4s.  Most seemed to stem from barrels overheating after extended full-auto firing (think a day of IA drills ). Some barrels did overheat so much that the front of the receivers warped and the barrels drooped, preventing the bolts from locking into the extension.  There were also issues with greatly reduced barrel life.  BUT, remember, this was after extended full-auto fire.  At the risk of sounding presumptuous, I don't think it would be an issue for most members of this foruom.  If I can find a copy of that report, I will post a link or fwd it to someone who can post it in its entirity.

I might be in the minority here, but I don't like the looks of the M4 barrel. It looks like it's pieced together from different barrels, IMO.

DW

Quoted: host146.ipowerweb.com/~initiali/pics/AR%20Burst%20Barrel.jpg This M4 barrel was on its 8th or 9th 30-round mag, fired in near-continuous full-auto, when the barrel ruptured.  As you can see, it did NOT fail at the M203 cutout (that is more common with SUPPRESSED M4 barrels fired on continuous full-auto, as heat builds up at the front of the barrel faster). -Troy

Also notice that the barrel failed before the gas tube did.  IIRC, gas tube failures happen mainly with suppressed uppers.

Or guns with crappy gas tubes from cheapo suppliers.