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Old January 4, 2012, 09:45 PM   #1
Dangerwing
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M249 barrel melt by blanks?

I am an OC/T in the US Army, and recently got into a "discussion" with another trainer. One of the soldiers going through our lane fired about 200 rounds of blank ammo through a M249 SAW cyclic - he never let up till the belt ran out. To avoid bias (and embarassment if Im wrong) I'm going to explain the argument in 3rd person, rather than identify which position was mine.

Trainer A felt that extended cyclic fire of blanks could damage a barrel just like extended cyclic fire of standard ball ammo. The reason being that the Blank Firing Adapter on the muzzle will keep the hot gasses inside the barrel causing heat to build and damage to occur.

Trainer B felt that extended cyclic fire of blanks will NOT damage a barrel because 1) the lack of bullets causing friction within the bore means drastically less heat will be produced and 2) blank ammo uses slow buring black powder that burns at a much lower temperature, thus again less heat will be created.

So, what do y'all think? Is trainer A right? Trainer B? Both? None of the above? Feel free to add your reasoning as well.

Thanks!
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Old January 4, 2012, 09:57 PM   #2
medalguy
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I've fired a lot of blanks in my years in and out of the service. I've never seen barrel damage due to blanks, whether a BFA was used or not. I HAVE seen serious carbon buildup after firing blanks, and if you shot live rounds right after blanks, without cleaning the gun, you'd have a big problem. But I don't believe blanks alone would cause any problems. And 200 rounds of even live ammo wouldn't hurt anything. I've fired quite a few 250 round belts of 30-06 and 7.62 in one continuous burst and not damaged a barrel that I could tell.
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Old January 4, 2012, 10:09 PM   #3
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It's not bullet friction that erodes the throat of a barrel, it's the high temperature flames of the gunpowder.

I doubt that they use black powder in those blanks but black powder makes a lot of heat. I sometimes wear a leather glove on my left hand when shooting black powder skeet with my old open hammer double because the barrels get so hot. With smokeless powder, they only get a little warm.
The corrosive fouling of black powder would wreak havok on the gas piston of a gas operated automatic weapon.
However, blank powder most likely is a special composition engineered just for blanks. Pulling the bullet from a live round and shooting it in a rifle makes for a blooper load without the resistance of the bullet's inertia to generate pressure.

I'm inclined to believe trainer A because a blank has just as much or perhaps more powder in it as a live round does.
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Old January 4, 2012, 11:15 PM   #4
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Remember that pressure is really the function there and not the heat of the powder in and of itself. The pressure and duration of the intense heat on the barrel would be more important. The blank adapter would increase pressure, allowing the rifle to cycle, but to the same degree as loaded ammo? I don't know for sure. Friction would also be a factor, I would think. I've not messed with blank rounds much, but if you're seeing that kind of fouling from them, I can think of one of two problems with them. The first would be that the rounds are using a dirtier powder, as the manufacturer isn't worried about accuracy. The second would be that maybe the lack of back pressure from the lack of a bullet in front of the expanding gas would lead to less complete combustion. This is all, of course, theory, hypothesis, guess, and what I thunk. The blanks are most likely not black powder, as the fouling from that would end the firing before that belt ran out. Check out some of the G&A videos (I'll try to find a link) of them testing black powder shells in a modern, semi-auto shotgun.
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Old January 5, 2012, 12:37 AM   #5
.45 Vet
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I don't believe the barrel would be damaged by the blanks. I am truely impressed that the DOD must have up-graded the training ammo. I never saw an old M16-A1 that would fire more than 1 or 2 twenty round mags of blanks before jamming. To think that the SAW would digest an entire belt is good news...
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Old January 5, 2012, 01:17 AM   #6
briandg
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for many reasons, I don't even remotely think you could burn a barrel with that.

there are a lot of complications to my thinking, but essentially, I feel safe in saying that there isn't enough heat value contained in the powder in the blanks to do it.

Can it damage the gas system? can it foul it badly? erode it some?

Blank powder is more explosive and generates a high pressure high gas charge.

if it had been harmed, you wouldn't be here asking.
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Old January 5, 2012, 02:29 AM   #7
R1145
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I've seen M16A1 barrels literally glowing red hot from firing blanks, so, yes, I think it is possible to damage a barrel using blanks.
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Old January 5, 2012, 05:52 AM   #8
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Is it possible? Sure, but it would take A LOT more than 200 rounds.
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Old January 5, 2012, 08:35 AM   #9
blume357
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Would it not be easy to do a test and find out...

fire 30 rounds of ball ammo in one rifle and check temp of barrel
fire 30 rounds of blank in an identical rifle and check temp of barrel
repeat a couple of times
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Old January 5, 2012, 11:04 AM   #10
Rob62
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I have fired LOTS of blanks through various full automatic guns during my time in the Army. And I can say without a doubt or reservation that they will not melt a barrel.

You can however get a barrel red/white hot by the continuous firing of blanks (or live ammo), and that this in and of itself does harm to the barrel metal.

Trust me when I say that you will by your own choice stop shooting long before the barrel gets anywhere near melting. The heat from a near white hot barrel is not something you will forget. And if you are any long term Machine Gunner, you will have some burns on your hands or arms from touching a hot barrel.

Side note - the longest continuous firing I did was about 500-1,000 rounds and the barrel while being VERY hot had not melted.
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Old January 6, 2012, 12:54 AM   #11
raimius
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I've seen about 1,000-1,200 blanks go through an M240B in 10-ish minutes. It wasn't glowing yet, but it was smoking for about 20 minutes afterwords. So, yeah, you could definitely damage a barrel with enough blanks.

200 in 5.56, probably not (my guess)...
1,000+ yeah...
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Old January 6, 2012, 07:29 AM   #12
blume357
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as a side note... my father was with a group of guys who melted the barrels on two browning water cooled machine guns one night in early Dec. 1950.
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Old January 6, 2012, 09:36 AM   #13
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I heard a whole lot of stories about melting barrels when I was in the military and could track down none. I would say the gun will jam long before that. I have seen the Belgian 240's when they started in tank turrets rip out loooong belts with out jamming. The German track guns are even more impressive. Sustained fire will eventually ruin a barrel, but melt one?
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Old January 6, 2012, 02:24 PM   #14
Willie Lowman
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A few years ago at KCR, DeGroat ran his minigun till I could see the barrels glowing from behind the firing line. Forget about melting barrels, I wish I had the ammo it takes to just get the barrel that hot.
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Old January 6, 2012, 02:29 PM   #15
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Ill go with A..

If I take my 257 WBY out and fire 8 or 10 as fast as I can it gets HOT.. Is it melting?? Id say yes at the leade..minutely.

When rifles are 'shot out' in couple thousand rounds--220 Swift had a reputation for that, I believe. What happened to the barrel to say it was 'shot out'?? Some (much??) of the leade and rifling will be gone.. How so--vaporized or melted?? Is there a difference?
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Old January 6, 2012, 04:31 PM   #16
James K
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One point, the powder in those cartridges was blaNk powder, not blaCk powder. Blank powder, contrary to the story, is very rapid burning smokeless powder designed to generate high pressure and make noise without a bullet in front of it. That is why blank powder must never be used to load cartridges with bullets; the extremely high pressure will destroy the gun.

IMHO, it would not be impossible for the heat from excessive firing of blank cartridges to damage the barrel, but I can't prove that. I do know I saw the barrel of an M1 rifle turn near white hot and begin to droop after about 100 rounds of rapid fire.

Jim
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Old January 6, 2012, 07:52 PM   #17
pvt.Long
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the barrel isnt damages with blanks as much as it is with live rounds.
" Trainer B felt that extended cyclic fire of blanks will NOT damage a barrel because 1) the lack of bullets causing friction within the bore means drastically less heat will be produced and 2) blank ammo uses slow buring black powder that burns at a much lower temperature, thus again less heat will be created." I doubt they use black powder is blanks. It is very corrosive and it doesnt burn slow it actualy explodes. Its deemed an explosive, that is why you cant go to bass pro and pick up a pound or two.
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Old January 6, 2012, 09:38 PM   #18
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Black powder is only classified as a low explosive due to its ease of ignition. It does not nor can it be made to detonate like high explosives. It burns so slowly that the "explosion" is nearly silent when a small amount burns unconfined.
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Old January 6, 2012, 10:53 PM   #19
Willie Lowman
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James, my encyclopedia tells me that steel is white hot at 2190 degrees. White hot steel is pretty much liquid...
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Old January 7, 2012, 07:21 AM   #20
B.L.E.
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The exact temperature of "white hot" depends on what your definition of
"white" is. Amber white, neutral white, blueish white. Ironically, photographers and artists refer to blueish white as a "cold white" and to amber white as a "warm white".
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Old January 9, 2012, 08:46 AM   #21
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Good post. Has me thinking back a few years. I am not sure what to say. I can remember a .50 barrel I checked with an erosion gage (A round tapered pin you stick in the breech end with rings cut in at intervals to check bore erosion) and it dropped all the way through the barrel and actually stuck out the other end a little bit. This was with a knurled section on the pin used as the handle. My point is : How could the chamber section (The neck area) get that worn with live rounds? I might add that this was an early barrel with out the stellite liner. I have seen various machine gun barrels with large chunks of rifling missing, but never one like that. Maybe there is something to the blank thing.
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Old January 9, 2012, 07:28 PM   #22
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There was some high speed footage on utube showing an m-16 firing full auto until the barrel failed, but that was live ammo.

I was an M-60 gunner and never fired that many blanks in a 60 or a m-16. I have seen them glow white from live ammo, but not melt.
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Old January 9, 2012, 09:23 PM   #23
B.L.E.
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Quote:
Originally Posted by Gunplummer
My point is : How could the chamber section (The neck area) get that worn with live rounds?
Like I said in an earlier post, it's not the friction of the bullets that erodes the barrel. There's just as much bullet friction at the muzzle as there is at the throat of the chamber, yet it's always the throat of a barrel that wears out first. That's where the powder burns.

If a muzzle does wear out, it's usually caused by cleaning rod abrasion.
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Old January 10, 2012, 11:57 AM   #24
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The neck area of the chamber is not really exposed to burning powder.
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Old January 10, 2012, 07:26 PM   #25
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Another point is that steel doesn't have to literally melt into a liquid before it fails. It's not hard to bend a piece of steel into a U shape if the center has been heated red hot. Heat a gun barrel red hot and the pressure of the gasses can easily stretch the bore oversized.
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