I have a Bushy Modular carbine, which has a free floating barrel that gets awfully hot while I shoot it. I try to rest the gun so the barrel won't get to hot, but I manage to make the barrel smoke. I load up about 4-6 mags before I get to the range, and I pretty much let go when I get there. The barrel is chrome-lined. I'm using XM193.

Question: How hot do I have to get the barrel to do any permeant damage? Can the barrel take the heat?  

I hear of heat damage a lot, so I was just wondering if I should be worried, or maybe it's just an issue with full auto.

Thanks


Edit:  Are there any tips on how to keep a barrel cool, or to help the barrel cool down. I will usually carefully stand the carbine up with the bolt locked open to let fresh air into the bore and to let the heat rise out. I can do this until my impatience gets the best of me and I load her back up and let the brass fly.

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Some things to consider:

1. Each round fired down the barrel will contribute to throat erosion.  The effect is accelerated when the barrel is hot.

2. If you get the barrel hot enough, the point of impact (POI) will likely drift.  It might be a temporary drift, or it might be a permanent drift (until next time?).

3. If you get the barrel up to 1100F, the metallurgy may change weakening the barrel.

At the ITRC this year, we shot approx 550 rounds in about 15-20 minutes.   This was got enough to turn stainless barrels slightly blue, and for aluminum gas blocks to expand and drift.   I cooled my barrel down with water from my camelback.

-z

Quoted: Question: How hot do I have to get the barrel to do any permeant damage? Can the barrel take the heat?

LOL! Much hotter than what you can do with 4-6 magazines.  You've got a Bushy - meaning a 4150 steel barrel which is the best kind of barrel steel to have if you like getting the barrel hot.

I hear of heat damage a lot, so I was just wondering if I should be worried, or maybe it's just an issue with full auto.

More an issue with full auto - unless you like to bump fire 100s of rounds at a time.

Note the Army indicates that  'cook offs' require a minimum of 140 rounds fired off really fast to even have a chance of a cook off.  And you have to get the barrel hotter than that to cause dammage.

Edit:  Are there any tips on how to keep a barrel cool, or to help the barrel cool down. I will usually carefully stand the carbine up with the bolt locked open to let fresh air into the bore and to let the heat rise out.

That works.  But if you keep your shooting to 12-15 rounds per minute you can shoot till you deplete Lake City's supply of ammo and not have a problem.

I have some Rules of Thumb when I’m shooting my Hollywood Horror.

If I can’t hold its barrel I wait until it cools down.
If it feels hot I wait.
If the barrel is lukewarm I shoot.
If the barrel feels cool I shoot.

While I do Mag Dumps from time to time, I’m more interested in accuracy than anything else.  That means that I’m not going to abuse ANYTHING.

Those Bushy chrome lined barrels are made to take a beating.......keep shootin!

Quoted:  I cooled my barrel down with water from my camelback. -z

I don't recommend that to anyone.   Water + burning hot metal = rapid cooling which warps the barrel.    And don't anyone say "what about the old water cooled machine guns" because those are in water the whole time, therefore the heat is disappated slowly, not instantly like 20 deg tap water on 500 deg steel.

20 deg tap water better call a plumber (lol)

if the barrel gets that hot air cool it,  like posted water is a no-no on real hot barreles.

I gotta wonder about cooling a scalding hot barrel with water as well.

Hbars I don't think I'd be overly concerned with but the thinner gov't. profile barrels seem like they have very little metal under the handguards with less rigidity.   And it's those gov't. barrels that get hot quicker thanks to having less metal and having less heat storing capacity as a heat sink.

Not sure if the rifling would be weakened by going through such a temperature change in such a short time, if the barrel were hot enough and quenched with water going through the bore it makes me wonder if the rifling of the barrel would be hardened and made more brittle.

Only reason I would quench a barrel is if I thought the dang thing was gonna get hot enough to run the risk of damaging my Surefire 500A but then if it were just blasting I was doing, I'd rather just put on a cheap set of carbine handguards and leave the 500A at home.  Let the barrel cool slowly like it should and cheap handguards be damned.

Cooling off a real hot barrel with water will degrade its structural integrity so at some point the steel will fail if its continously done.Its like any thing else if you had to use it for defense your not gonna dump unless your covering movement or to break contact otherwise single aimed shots are the order of the day.

Quoted: Quoted:  I cooled my barrel down with water from my camelback. -z I don't recommend that to anyone.   Water + burning hot metal = rapid cooling which warps the barrel.    And don't anyone say "what about the old water cooled machine guns" because those are in water the whole time, therefore the heat is disappated slowly, not instantly like 20 deg tap water on 500 deg steel.

I don't do this on a regular basis, and I agonized somewhat over the impending barrel-burning stage, heaving heard reports from the guys who shot it the first day.   I didn't want to ruin my $2000 match AR, of course, but I couldn't switch guns and I had to finish the match.  

A guy with the same upper had a problem the first day where the aluminum set-screw gas block expanded and slid down his barrel turning the action to single shot.  I didn't want that to happen.

So the only seemingly reasonable thing to do was to douse the gas block and the forward part of the bbl with water periodically during that hose-fest.  

In the end, the barrel's POI migrated about 2.5", and it shoots about like it did before.  

Here's the full match report:
brianenos.ibforums.com/index.php?showtopic=16277

-z