I've heard the various terms used on this board, such as "it's okay to do X, Y and Z as long a you don't engage in an abusive amount of rapid fire."

Can anyone quantify for me what an "abusive amount" of rapid fire would be for a preban Colt carbine?

60 rounds as fast as you can pull the trigger?  90?  300?

When does the fun stop and damage really begin?

If time allows I like to let the BBL cool to the point where I can rest the back of my hand on it, before I run another 20 rd mag thru it. -- I have run 120 rds thru a M16 ASAP on full auto, but it was govt. issue and at the time I did'nt care about resale value. -- You'll smoke the finish before you do any real damage to the steel in the BBL. -- Just my $.02 -- ALLONS11

You can't over shoot it. Your finger will burn out way before your barrel does. On my bushie I have tried to rip off 12 mags (27 per mag) and the only thing destroyed was my gun gase when I put the gun to rest after I accidentally put it on my shoulder. Some people trip when I do this "gooks are in the wire" thing, except class 3 guys, but Hey! sarco barrels are only $130 and I dont think I will burn mine out anytime soon though. Never had a cook off and never seen one.
GG

I'm just taking a stab here (I have no scientific evidence to back me up, just a lot of experience shooting in full auto), but I think about 3 mags either rapid fire or full auto is about the point where you have sufficiently heated the barrel to start causing some real wear.  The more rounds you put through it in rapid succession, the hotter it'll get.  The hotter it gets, the faster your barrel will wear out if you keep putting rounds down it.  Just as an example, I've seen guys go thousands and thousands of rounds with the same barrel in a Browning 1919 if they shoot conservatively, but I've also seen guys make smoothbores out of 1919 barrels in about 3-5k when they really hammer on them and just dump belt after belt. Also, depending on the manufacture and quality of your parts, somewhere around 100rds is also about the point where you're really starting to heat your gas tube.  Firing full auto, either in 30rd mags, back to back, or with beta-c's, most gas tubes will fry between 100-200rds.  I've seen some go far less though, with inferior parts.  When I'm shooting, I'll usually blow through 1-3 mags in short bursts, and then put it down until it cools a bit.  You will start to damage your barrel well in advance of any cookoff.  Just remember, its a rifle, not a SAW or LMG.

It depends at what level you want your rifle to function.  I would never rip off a full clip out of my 24" stainless match upper, but with a chrome lined M4, who cares about pinpoint accuracy.  If you want to hit man size silhouettes at 25 yards, blaze away, but the heat from one 20 round clip at rapid fire will begin to heat crack the throat of the barrel.  If the barrel is smoking, you can bet on heat cracking of the bore up to the muzzle and loss of leade.  However, unless you are a benchrester, so what?  As long as the rifle hits an acceptable target size, rapid fire is what the rifle is designed for, and like another poster says, new barrels are cheap.  Just be aware that Rambo imitations will bring a new barrel on sooner.  Hey man, it's all fun.  Fire away.  

I don't own any M16s but I have shot the ones other people have generously stuck in my hands to the point where the handguards were too hot to hold.  At least the owner of the M16 didn't seem to care or think this was unusual.

I don't think I could heat one of my semis up like that no matter how hard I tried (or how fast I worked my finger).  I wouldn't worry about it unless I had a spacegun with a big scope on it.

Quoted: I don't own any M16s but I have shot the ones other people have generously stuck in my hands to the point where the handguards were too hot to hold.  At least the owner of the M16 didn't seem to care or think this was unusual. I don't think I could heat one of my semis up like that no matter how hard I tried (or how fast I worked my finger).  I wouldn't worry about it unless I had a spacegun with a big scope on it.

I once called Quality Parts Corp/Bushmaser up on their 800 number and asked them precisely this same question.  They said "in semi-auto mode, there is no way that you are going to pull the trigger fast enough to over heat and destroy a barrel, but he also aaid that in full-auto it would be different story.