I was thinking about putting together a really light carbine. I already have a Cav Arms MkI lower, which I'll upgrade to the MkII. Thinking about getting a BM superlight upper for this lower.

Anyway, is there a limit to how many rounds I can shoot safely through this upper at one time?

I know light barrels heat up more quickly. So, could you tell me is there a danger involved (or possible damage caused to upper) if I shoot say, 500 rounds at a range session?

Only one round at a time.

RATS!

curt you beat me to it.

Smartass! [:D]


I meant how many rounds at one range session. Duh! LOL

17.

Any more and the barrel will spontaneously melt into a puddle at your feet.


Seriously...it all depends on how fast you're shooting.  Are you bump firing?  Slow, aimed fire?

Excessive barrel heat from long strings of rapid fire with back to back mags will increas throat erosion.  Odds are if you dont bump fire a beta mag your safe.  You will melt the gas tube before you melt the barrel.  If you think the barrel is too hot pour some water on it from your water bottle and continue.

I shot 300 rounds pretty rapidly through a Bushy SLW barrel while testing some Brit steel mags from ammoman.

The handguards were too hot to hold at one point. No problems with the upper (or mags). The SLW profile is just as skinny under the handguards as the M4 or A2 barrel.
[BD]

I had a CAR15 in Vietnam and shot 500 rounds through it in 10 minutes, maybe less, many times.  Nothing happened and it always worked up to that point.  After 25 mags I knew I better start getting the cleaning rod ready to clear the chamber from double round jams.  Just don't touch the barrel or try to be a sniper.  I built a cav MKII with a 19 inch colt pencil barrel I got from SARCO for 135 bux.  had to cut the threads off and put on a 11 degree crown but it works great.  I have no problem making 15 inch groups at 300 yards.  Weighs 5.8 pounds.  I like the longer sight radius and higher velocity of the longer barrel.

bar

What was the twist of the barrel?

Bob

clean_cut, you will not be melting your barrel down, the gas tube would melt far before your barrel would even get close.  Your accuracy will diminish when the barrel starts to flex, but that's it.  You will errode the throat in a more accelerated manner.  I use the BM LW 16" in a recent build and when it gets too stinkin hot I just lay it down and transition to another firearm.  Your lube will smoke, and it will be too uncomfortable to hold, but it still won't seriously damage your barrel.  Shoot 10,000 rounds while you are at the range, it will be virtually no more wear than 10,000 on any other barrel.  Now if you are using it for full auto, and are firing continuously, or as much as you can, you'll melt your gas tube after a C-MAG and a few more 30rd mags worth.  Remember, the original M16 used the pencil barrels.  So fire away and don't worry about it, but let it cool to recover accuracy, and comfortability (is that a word?) when holding it.  Don't go dunking it in a bucket of water to cool, you will do bad things to the metal.

Cook-offs of the M4 have happened with as few as 210rds full-auto in a short time period and they get pretty unpleasant to handle as well even with double-heat shielded handguards.

How did you avoid both of those issues when firing twice the amount of ammo out of a barrel with less mass that would heat up faster?

I did three days at Thunder Ranch in the June, Texas heat with no problems.

[img]http://www.hunt101.com/img/079868.jpg[/img]

concerning:

"Cook-offs of the M4 have happened with as few as 210rds full-auto in a short time period and they get pretty unpleasant to handle as well even with double-heat shielded handguards."

"How did you avoid both of those issues when firing twice the amount of ammo out of a barrel with less mass that would heat up faster?"


I didn't do anything to avoid the issues -- I just didn't encounter them. I was careful to  not touch the hot metal but that was it.  never heard of a round cooking off with anyone, ever.  

Your biggest danger from dumping LARGE quantities down range RAPIDLY would be throat errosion.


I doubt seriously ANYONE has seen a cook off in semi-auto fire.

210 rounds in under a minute and 500 rounds in ten minutes are miles apart in heat buildup.  Thats like asking someone how he kept from blowing his engine by revving it to 6000 rpm for 5 minutes when revving for a minute at 9000 will blow it.

Maybe you were cooking off, you just didn't know it or care at the time. If you know what I mean. [LOL]

Question...
Is the BM SLW barrel the same "size" as the old M16A1 barrels?

I seem to remember that it is, and if so, I have seen these "SLW" barrels fired very rapid with live ammo and blank ammo.

In fact, I blew off 210 rds of blanks in under 2 min and all I got was a red gas tube out of it. I was still able to qualify expert a week later.

Those old "SLW" M16A1 barrels took a pretty good beating and still passed arms room testing.

Am I wrong with the SLW and M16A1 diameter comparison?

'Close enough for Government work'  (heh!)

KY-Bob, during the Vietnam War the barrel twist at that time was 1x12.

I was referring to the SARCO barrel. Sorry I didn't make that clear. I have since found out that the SARCO barrels are also 1/12".

Thanks,

Bob

I once fired 10 30 round mags from an M-16A1 as fast as I could reload (pulled the trigger ten times, basically) and later qualified expert with the same rifle. Should be OK to shoot yours a lot. Remember, the M-4 barrel is a 'pencil' under the handguards, too.