Some Questions about M2 Machine Gun

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numaone

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Fellows,
I am looking for some information on the M2 Browning Machine gun they have on top of HUMVEEs. I see that they are air cooled, but they have a maximum number of rounds that can be fired before "damaging the barrel." I assume that's because the barrel gets too hot. Anyone know how hot the barrel gets after X number of rounds? Why don't they have water cooled barrels on the M2’s Mounted on HUMVEEs? What is the maximum temperature the barrel reaches?

Do you guys know the outer diameter of the barrel? How about the material? Is it a carbon steel (1010, 4140 series?) or is it stainless?

Thanks for the help,
Numaone
 
I believe that the .50s have Stellite liners in chambers and the first few inches of bore for heat resistance and durability. I don't know the numbers, but it is possible to heat a M.G. barrel red hot.

The water cooled M.G. is pretty much obsolete, mobility is more important these days than sustained fire.
Sustained fire: When presenting the 1917 .30 cal water cooled M.G., Mr Browning personally sat down behind one and held the trigger down for 46 minutes. About 26,000 rounds at the stated rate of fire for the gun. Why 46 minutes? Because they did not have enough ammo belted up for the hour demonstration he wanted.
 
All machineguns have three rates of fire.
The Cyclic rate is how many rounds per minute they will fire if the trigger is held.
For the M2, it is 450-575 rounds per minute. Given enough ammo, you could melt the barrel if fired at the cyclic rate for long enough.

The Rapid fire rate is more than 40 rds/min, fired in bursts of five to seven rounds. This would only be used in an emergency.

The Sustained fire rate is Less than 40 rds/min, in bursts of five to seven rounds. This would be used for normal operations and you would likely run out of ammo in a HumVee before burning the barrel up.

All modern air cooled machineguns have quick-change barrels, and the barrels are supposed to be changed out before they overheat. Note the wire handle on an M2 barrel to allow removal & barrel change when it is too hot to touch.

M2 barrels are made from carbon steel and are Stellite lined to prolong their life during sustained & rapid fire.

rc
 
Too hot to handle with your bare hands!!

I don't know the exact temp, but we are not talking glowing white hot or anything.

The thing is, it's not that big of a problem or we wouldn't still be using the M2 almost 90 years after it was adopted by the military.

rc
 
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Too hot to handle with your bare hands!!


I used to like to watch the "Rat Patrol" where the guys would be shooting a 50 mounted on a jeep and just grab the barrel to turn the gun around.
 
All modern air cooled machineguns have quick-change barrels, and the barrels are supposed to be changed out before they overheat. Note the wire handle on an M2 barrel to allow removal & barrel change when it is too hot to touch.

The M2 does not have a quick change barrel. It must be unscrewed, the wire handle has a lug on it that you slide into matching slots on the barrel and turn. The new barrel must be screwed in and the headspace and timing set. This isn't exactly quick change.

FN has made a kit that converts the M2 to a fixed headspace gun, but the US has never adopted it.

According to TM 9-1005-213-10 on page 1-10 the barrel change rates are as follows:

Single Shot: Change the barrel at the end of the firing day or if the barrel is damaged.

Slow Fire: Slow fire is less then 40 rounds per minute, fired in bursts of 6-9 rounds, at 10-15 second intervals. Change barrel at the end of the firing session or if the barrel is damaged.

Rapid Fire: Rapid fire is greater then 40 rounds per minute, fired in bursts of 6 to 9 rounds, at 5-10 second intervals. Change barrel at the end of the firing session or if the barrel is damaged.

Cyclic Fire: This rate represents the maximun amount of ammunition that can be expended by a gun without a break in firing. The cyclic rate of this caliber .50 machine gun is 400 to 550 rounds per minute. Change barrel at end of firing session, or if the barrel is damaged.
 
I can't quote a temp but they get really hot. Way too hot to touch.

I've seen 240 barrels glow at night if that's any indication for you.
 
Naw...I watched Rambo, the latest one, and he was running a 50 sustained, through not one, but two boxes of ammo and the barrel never even smoked, much less exhibited that pureena glow!

Good effects in that movie.....

must have been down loaded ammo...?!? lol hehehehe
 
Do you guys know the outer diameter of the barrel?

On Mythbusters (now there’s a reliable source) they tested the myth of Japanese soldiers in WWII slicing red-hot machine gun barrels in half with samurai swords. The used an old reused barrel that looked about .30 caliber, and the wall thickness looked to be a little greater than the caliber.
 
I can't imagine changing Ma Deuce's barrel under fire. You'd have to hop out of your nice, armored turret with the asbestos mitt, unscrew the barrel, which weighs the better part of 50 lbs, and then replace the barrel and fiddle with the headspace gauge. Although your spare barrel(s) should already be matched to the gun, so you shouldn't need to fiddle much. Likewise timing.
 
Water-cooled guns on vehicles isn't a bad idea, since you don't have to carry the weght yourself. however, I don't thing you could carry enough ammo to make it worthwile. And yes the old water-cooled guns are very cool, because firing for that long is cool, in a stupid sort of way.
 
The Vickers machine gun in 1967 the british Army fired 5 million rounds out of one just for the hell it really. As you do the .303 rounds were going out of service :D gun was still fit for service.
5,000,000 Rounds in Seven Days and Seven Nights - to Prove a Point ?

Obsolete or not, there was strong attachment to the Vickers. Many felt, why get rid of something so good? As if to prove a point (and also to use up the Mk VII ammunition still in the inventory, which was no longer approved for Service use), the most exhaustive trial probably ever fired from a Vickers took place in 1963 at Strensall Barracks in Yorkshire, England. Five million rounds were fired from a single Vickers which was kept in constant use for seven days and seven nights.

British Army Sergeant T.R. Ashley was one of nine armourers involved. At the time he was in an 18-day Vickers course at Strensall Barracks. As related by Sgt Ashley op Warren Wheatfield of Sudbury, Ontario.

".. First day, gauging limits and setting the gun up. (We spent two days hand filing feathers [the square projection] on cross pins to close tolerances so guns and tripods could be assembled without play!) at the end of the day, the instructor told us to draw out one of the guns that we had been working on, [and] one of the lads pulled a gun out of the rack. We were told that this gun was to be fired for the remainder of the course, day and night.

The gun, stores spares, etc, were put onto an Austin Champ and driven onto the range. We mounted the gun onto a tripod in a gun pit. A 4-ton Bedford had been unloaded with ammo. There were stacks of ammo, after cans and barrels. (We had to pack all the rear groove with asbestos oiled string!) The 2 man crew was relieved every thirty minutes. A third body shovelled empty cases from under the gun with a malt shovel and threw the empty belts clear of the pit. We never heard the gun not firing in anything but the shortest time while the barrel was replaced (every hour). The gun fired 250-round belts without stopping: not in 20, 50 or whatever bursts, but straight through: we could hear it rattling away from the lecture room/workshop, and went to see it between work.

At the end the gunpit was surrounded by mountains of boxes, belts, cases, debris; a large cleft had appeared in the stop butts where the bullets had destroyed the butts. We took the gun off it's tripod and back to the workshop. We inspected and gauged. No measurable difference anywhere. It had eaten barrels, they were changed every hour to 1½ hours, but mechanically [the gun] was unchanged. It had consumed just under five million rounds of .303", non-stop (my notes were for Mk VII, not Mk VIIIz, so I presume zones etc were for Mk VII).

That episode was to show nine armourers the ability of the hallowed Vickers. Only after an excellent course result did my Staff Sergeant boss let me work on our battalion guns, which had smooth waterjackets.."
 
No need to swap barrels on the .50 in combat... I fired over 12,000 rounds between two guns (mine fired about 8,000 of them) in one morning and only changed the barrels every 1,000 rounds or so. The barrels were hot but not "glowing" or anything... these are M2HB's (HB= Heavy Barrel) they can take the firing.... no problems.

Once the firing was done and weapons were cleaned there was hardly and visible wear (my gun was brand new out of the crate) and we only had 3-4 stoppages which was due to that one can of ammo had been issued out and the links had gotten rusty. Switched cans and it didn't jam again...except for the French .50 cal that stuff was crap and was full of duds and hangfires...THAT ammo went into the demo pile....

Pics of my gun truck...
DSCF0859a.jpg
 
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I typed out a nice long reply and then lost it when the server was too busy to post!!!

Anyways to sum it up, my company had a .50 cal day where everyone shot a box through one of two guns. The humvee gunners shot a lot more. The barrels got really hot and one poor guy grabbed it getting out of the truck. He was rushed to the ER and had to get skin graffs (spelling?) on his palm.

As far as durability of the weapon, in 2005 one of our .50s had a four digit serial number. That thing had to be pretty old but it still ran like a champ.
 
The weight of a standard M2HB barrel is 24 pounds, IIRC.

I do recall reading a while back on another forum some interesting files from WWII regarding 200rd tombstone drums used in turrets onboard carriers in the Pacific. From what I recall, after a full drum dump at cyclical rate, the barrels were trashed (although I believe they were a lighter AN M2 or M3 setup, rather than an actual M2 Heavy Barrel design). The photos of bulged apart bores were pretty graphic...wish I'd saved them.
 
Anyone who has been through dissassembly and assembly of the M2HB will understand why this weapon is still in use after 90 years. Like the M1911 it was built to last.
 
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