I'm thinking of getting a kit in the near future with a lightweight barrel.  I would be using it for hiking  in the desert.  How many consecutive rounds can you fire on a lightweight barrel before the barrel gets to hot to shoot it safely?  Would shooting 5, 30 round mags consecutively be unsafe?  I was just wondering how the lightweight barrel would stand in a SHTF situation.

Thanks,
556man

I have probably shot that many rounds fast through an M4, and no its not unsafe. Its nowhere near the temperature required to cook off a round. It will heat the metal parts of the rifle to dangerous temps. I suggest you consider a vertical forgrip or carbon fiber free float tube to keep your hand cool, and be VERY careful not to touch the barrel.

Thanks for the info and tips Combat_Jack.  That's fine with me as long as it's safe to shoot 5 30rd mags consecutively.  I guess in a firefight the battle should be over before I use 5 30rd mags "God forbid".  I'm going to try this lightweight kit so I could travel light during hiking around the desert here in Las Vegas.  Thank God summer is over.

556man

Get a chrome barrel, they handle heat better.

How on earth is a chrome barrel going to handle heat better? Does it contribute to structure? Does it have increased thermal capacity? What, is a chromoly barrel going to catch fire? Stop spewing crap.

I've got a LW barrel; it performs as well as the HBAR I had earlier. Your only possible danger is, as stated, cookoffs. LWs heat up faster, but they cool faster, too.

Quoted: Get a chrome barrel, they handle heat better.

What's up with that Jack, chrome is good in a lot of ways but how do they handle heat better ?

Dont worry about overheating... noone here has ever had a cook off I have heard of with semi auto use / abuse.

Quoted: How on earth is a chrome barrel going to handle heat better? Does it contribute to structure? Does it have increased thermal capacity? What, is a chromoly barrel going to catch fire? Stop spewing crap. I've got a LW barrel; it performs as well as the HBAR I had earlier. Your only possible danger is, as stated, cookoffs. LWs heat up faster, but they cool faster, too.

Not short term, idiot, the throat lasts twice as long.

Quoted: Quoted: Get a chrome barrel, they handle heat better. What's up with that Jack, chrome is good in a lot of ways but how do they handle heat better ?

Like I told the Llama, the throat in a chrome bore lasts twice as long before its burned up and you lose accuracy and even velocity.

Listen, BOY, that's not handling heat better, that's gas erosion resistance.

Quoted: Listen, KID, that's not handling heat better, that's gas erosion resistance.

What I mean, is that the barrel handles being heated up and fired hot better, it lasts longer. As far as how hot it gets during firing, I suspect the difference is negligible.

So you've just discarded your point?

You claim "Get a chrome barrel, they handle heat better."

What does "handling heat" mean? How does a chrome barrel "handle" heat better versus an unchromed barrel? What mechanism permits it to "handle" heat better?

Do you honestly think the ambient substrate temperature really matters when you have the burning gasses above at supersonic speeds?

Edit to simplify.

What I mean is that the chrome lining doesn't burn out nearly as easily as the chrome moly barrel. This means a longer service life. Plus, out in the boondocks he won't have to worry about moisture in his barrel, at least not nearly as much as with an unlined barrel.

This is some stupid shit to argue about

Good, so you're finally free of this "handles heat better" crap.

No, it's not stupid shit to argue about, because you're spewing stupid shit.

Chrome lining's importance is far, far, overblown for civilian applications.

Quoted: It will heat the metal parts of the rifle to dangerous temps. I suggest you consider a vertical forgrip or carbon fiber free float tube to keep your hand cool, and be VERY careful not to touch the barrel.

A nomex flight glove can do the same thing...worked great during rapid fire of my old Sterling AR180...

Am I going to have to separate you two boys?

Quoted: Good, so you're finally free of this "handles heat better" crap. No, it's not stupid shit to argue about, because you're spewing stupid shit. Chrome lining's importance is far, far, overblown for civilian applications.

I never claimed that there was ANY difference in how they heated or cooled based on the lining. I don't believe there is. The fact of the matter is, a chromed barrel will outlast by twice or more an unlined barrel. Especially in a lightweight barrel that is shot hard.

Quoted: Quoted: It will heat the metal parts of the rifle to dangerous temps. I suggest you consider a vertical forgrip or carbon fiber free float tube to keep your hand cool, and be VERY careful not to touch the barrel. A nomex flight glove can do the same thing...worked great during rapid fire of my old Sterling AR180...

True. I like the vfg cause there is no way you are going to touch the fsb and get a burn while you have your hand around it.  I have had the delta ring get pretty hot on me too.

Getting back to the original question, you won't have any safety problems dumping 5 30 rd mags out of a lightweight barrel.  Consider the following:

1) The weight of the barrel on the A2 is actually the same as the A1 under the handguards.  It' sonly heavier out front.  Since these are the two profiles used the by the military, who tend to dump alot of ammo quickly out of barrels, then there's probably no safety problem.

2) Just think about how many rounds were shot out of barrels in Vietnam.  Thoses were lightweight profile.  I personally know folks that have shot far more than 5 mags out of an M16 on full auto and not had a problem.

3) I've shot the M16A1 on full auto enough to get the gas tube to glow read.  The rifle will contiune to function and be safe to fire.

4) You're rifle will most likely cook-off before any other problems.

5) You're gas tube won't burst.  See the thread on barrel testing to destruction.  Or do any ohter research on the matter.  Barrels burst before gas tubes.

For a SHTF scenario, the lightweight barrel is fine.  You'll either be out of ammo, out of targets, or out of luck before the gun blows up (provided you have a quality build).

Ross

Thank you all for the info and tips. Appreciate everybody's input.  I will be getting a Model 1 with a lightweight  chrome lined barrel.  Chrome lined barrel should last longer than a chrome moly barrel plus it's much easier to clean.

556man

A gov't profile M4 barrel will get hot enough to begin cook-offs after about 180-200 rounds fired consecutively(full auto).
In our tests, the M4 barrel was between 900 and 1000 degrees F, 3" forward of the chamber, after 180-200 rounds in full-auto.
Cook-offs began, and in both tests there were 2 cook-offs between 24 seconds and 85 seconds after ceasing fire.
A standard M4 barrel in 155 degree F ambient temps had 10 cook-offs after 200 rounds fired continuously, and was still cooking-off after 2 minutes of cooling time.
These were GI M4 barrels, chrome-lined.

If you bump-fire 5 mags, you will be getting very close to cook-off temps. On a hot day in the desert, you may even get some cook-offs after 5 mags rapid-fired.

Heavy barrels fared much better, going from 220 rounds to 260 rounds before reaching cook-off temps.

These were laboratory condition tests, with heat sensors positioned every inch along the barrels.


Tom Lyons
MGI