Weapon *Life Expectancy*

You must mean 2,500 fps in regards to the 172 grain M1 Ball round.

 

You are correct should actually be 2,600fps+, that's what happens when you don't proof read and start typing quicker than you are thinking

 

No problem. Also remember large capacity cases don't burn up all the propellant instantly. So, you've got gas and flame from ignited propellant chasing unburnt powder and the bullet down the bore. That unburnt powder also causes damage to the bore.

 

Hmm, you can't seem to make up your mind.

Clearly your memory is as faulty as your "facts". All that "erosive stuff" appears to be highly corrosive.

HAHAHAHAHA!!!!! Ever been to Knob Creek or a war zone? I've continuously burned up more ammo than the figures you listed. Ever see BreakFree self-ignite on a cherry red M2HB?

Wrong. If you actually had a reference library, you'd know. I like your prefacing your water-cooled MG opinion with an admission of minimal experience. Yet, experience is the key to forming opinions-- according to you.

Summing up, you have little experience and no sources to back your "conclusions". You asked me to educate you. You've been schooled. I'll let jughead take over summer school.

 

Ofcourse I can, but as you should know different dimensions doesn't refer just to barrel thickness. For an MG & rifle barrel to be interchangeable they would for starters need to use the exact same dimensions at the breech.

No it's also very erosive thanks to the high flame temperatures I'm afraid.

Are you talking barrel life in terms of keyholing to downright jamming here, or just till noticable loss of accuracy like I am?

I have a very nice reference library actually, problem is that at the moment I am not at home with it, so I'll have to rely on memory for now in addition to what I have on the portable. So lets get the dimensions for the M1919A6's barrel thickness vs the M1903's then.

Ah, so smug, you gotta love it..

 

Yeah, it was 2,665 fps for the M1 Tracer and 2,640 fps for the regular M1 Ball (assuming it is similar to the M72) according to this place: .30 Caliber (.30-06 Springfield) Ammunition.

 

'Sustained Fire' is not the same as 'cyclic rate of fire'. Rifle barrels are designed to operate within specified parameters (cyclic rate); exceeding the design parameter will cause undo wear and decrease the service life of the barrel causing it to fail.

 

Spot on. And in combat you often exceed these parameters.

As for the test of the M1917 MG, here obviously all such parameters were completely ignored, the gun being kept firing for nearly an hour. And I bet the barrel was shot out before the first 10,000 rounds, reaching even half that with continuous fire is extrememly impressive. The barrel of an air cooled MG can be ruined in less than 1000 rounds.

 

This document lists the rerquirements for the M240B.
PRODUCT REQUIREMENT FOR 7.62MM M240B MACHINE GUN Revision 10 17 ...
on page 8 it states a minimum of 15,000 rounds and one of the failure critieria is a drop in mv of 200 fps
This page: USA 0.50"/90 (12.7 mm) M2 Browning Machine Gun (BMG) lists the air cooled version of the M2 as having a life of 3,000 rounds but rather implies that the water cooled version had a significantly longer life.
This link: Ordnance - Google Books
Suggest that bullet errosion is more important that gas erosion in machine guns and mentions life times of 15,000 rounds or more and specifically states barrels with over 17,000 rounds shouldn't be considered wothless except in certain cirumstances. It's worth noteing that this is a 1920 document.

 

Which is exactly why the military trains the way it does. Machine gunners and Riflemen are not just handed a rifle and told 'good luck'; they train in a little thing called 'fire discipline'. Any chimp can go out and hose the battlefield and the only time it is endorsed, hosing the battlefield, is during the 'final protective fire' while in the defense.

Please do not speak to me of 'combat' unless you are the primary source for reference. I have that t-shirt (BTDTGTT) and I am not necissarily intrigued by the meusings of someone who does not.

The M1917 test was to prove the 'action' of the weapon, to see if it could withstand prolonged fire without a stoppage in it's cycle of operations.

You are providing a different context to the information you are citing and it is beginning to annoy. It's clear that you have a grasp of the information and technology, just not the application of principles. I think you would be better served if you asked more questions instead of stating fact.

Here is a pretty good article on 'Rates of Fire'
Rates Of Fire

Here is another on 'Fire Discipline':
http://defensetech.org/2009/10/14/or-is-it-bad-fire-discipline-and-leadership/

Here is a link to the current FM on operation of the M2 HB:
FM 23-65 Chptr 5 Marksmanship Training

Anything can be ruined if it is not operated properly, regardless of application.

 

I am having certain difficulties in understanding your standards for a barrel beeing 'shot out'.

You seem to have the same standards for both a bolt action rifle and a mg. Accurancy as the most important.

For a rifle accurancy is the most important bit, but that doesn't go for a mg.

I'd rather flip it and say lower accurancy on a mg barrel equals better accurancy. I am refering to the 'cone of fire'.

 

I have been following this thread but have avoided posting because I didn't want to get drawn into another of these threads where we go round and round with no resolution and information is put out that is complete BS.

O.K. 8 years 9 months spent as an 0331 Machine Gunner in the Marine Corps. 6 months of that spent at SOI (School of Infantry) instructing in the theory, employment, tactics, techniques, maintenance and first echelon repair of crew served machine guns which were then in the Marine Corps inventory.

You apparently don't know what sustained fire is, here's the definition:

sustained rate of fire the actual rate of fire that a weapon can continue to deliver for an indefinite length of time without seriously overheating.

As Brad said earlier, the M-1917 was water cooled, as long as sufficient water was available to keep the barrel from overheating it could fire at it's designated sustained rate indefinately.

Why? It's documented, if you're going to dispute the results of the test then it is incumbent upon you to provide information to show the test was falsified.

You are greatly overstating the effects of corrosive ammunition. It's the corrosive salt reside that is the problem and it's effects, upon metal, do not manifest themselves immediately. If you do not perform basic maintenance, yes, over time it will damage the metal but not within the time parameter of the quoted test. Did you know that simply pouring hot, or better yet, boiling water down the bore will remove most of these salts? Run an oiled patch, a patch with some RBC or some CLP down the bore, follow with a dry patch and you have counteracted the effects of the ammo. Simple huh! Keeping your weapon clean is something that is done continually, not just before you store it away until your next collector's meeting.

Well here you are correct, it can be ruined in 1000 rounds. In practice this is unlikely unless you're untrained and rode on the 'short bus' to the firing range.

Wrong! The M-60 normally comes with two barrels, one is a spare. Under sustained fire depending upon the rate of fire the barrels, as a rule of thumb, will be swapped at between 250-500 rounds so the barrel being used can cool. The barrels will continue to be swapped back and forth as one cools and the other is heated by firing. The barrel itself has an average life, IIRC, of around 25,000 rounds. If you are firing three to five round bursts with sufficient pauses between bursts, you won't need to swap the barrel until the 500 round point. Longer bursts with shorter pauses and you'll be closer to the 250 round point. Given sufficient ammo and swapping the two barrels back and forth, before they become overheated and you can do this for a long time.

Actually the Army Manual (FM 3-22.68) is much more specific:
Rates of fire
Sustained– 100
Rapid –200
Cyclic –550

Barrel Change interval
Sustained rate of fire- every 10 minutes
Rapid rate of fire- every 2 minutes
Cyclic-every minute

So you can see how rate of fire, not number of rounds fired determines how frequently the barrel must be swapped/changed (not replaced). 1000rds at the sustained rate, 400 rds at Rapid and 550 at cyclic. I guess I need to clarify the definition of cyclic rate:

The maximum rate of fire of an automatic weapon (the cycle rate) is defined as the maximum number of shots per unit of time that the mechanism of a given model of a weapon permits.

 

No you're right, apparently I didn't. Sustained to me meant what the word usually means. Different places, different wording, what do ya know.

What is documented? That the barrel lasted for 20,000 rounds of continuous fire? I think the only thing documented is that the action lasted the 20,000 rounds, which is entirely believable - infact it would be quite odd if it didn't.

That the barrel lasted for 20,000 rounds of near non-stop firing is quite simply unbelievable however, watercooled or not. Are we seriously in disagreement on this?

Well when I said sustained fire I did mean non-stop, no pauses, and the throat of the barrel is definitely not in good shape after 500+ rounds then (aircooled). I remember seeing an M60 glow red hot after firing a similar number of rounds, needless to say the bore had taken quite a beating. I also quite clearly recollect an MG3's barrel reduced to junk in a very shot space of time, can't remember the shot count.

 

But again, we're talking about one long continuous burst in this discussion - at least I am. And not many MG barrels will last very long then.

The debate has however now instead been turn upside down, people now discussing the barrel life of machine guns if properly operated. The debate was never about this, the M1917 in the test clearly not being properly operated with a view on maintaining barrel life, and this has never been disputed.

 

That seems fair enough to me, so now we're on the same page and we'll move on.

Yes, we still are in disagreement, but that could be because I didn't make myself clear enough in my previous post. The only reason that barrels were changed/swapped out in guns like the MG42 or M60 were for cooling not barrel wear. Heat from the propellant gasses, not friction is the predominant factor. That's why I presented the data on the different rates of fire, it's not the total rounds fired it's the rate at which they are fired that determines barrel wear up to the designed barrel life.
Example: Theoretically at the sustained rate of 100 rounds per minute, and swapping the two barrels every ten minutes, you should be able to contiuously operate the M-60 machine gun up to the 25,000 rounds per barrel with no appreciable loss of accuracy. Now in real life other factors creep in, ambient temperature can effect the barrels cooling rate, or carbon buildup in the gas port will cause the gun to run away or lack of lubrication will cause a mechanical part to fail.
In the M-1917 the heat factor is minumized by the water cooling the barrel and keeping the temperature of the barrel within it's designed operating parameters. So it, theoretically, should be able to operate continuously up to the designed barrel life (which I don't pretend to know) as long as there is sufficient water to keep the barrel cooled to it's designed operating range.
I think it has already been mentioned but it's just like a car, as long as the cooling system keeps the engine cooled to the proper operating range it can, theoretically, drive indefinately, given enough fuel, up to the given designed mileage of the engine.

I've seen the same thing but you're talking aircooled vs. water cooled, barrel temp is the key factor. Water cooling mitigates the temperature factor.

 

But the test was not being conducted to see how long the barrel would last; it was, in fact, a test of the operation and function of the gun: ie How long the gun could go before it suffered a jam or other failure in the cycle of operations, accuracy was not in the test paradigm.

 

That was the point exactly Brad, and since it was using cloth belts, I would assume there were any number of belts rather than one continuous belt with 20,000 rounds in it. While that wouldn't be much of a break between belt re-feed, the test was on the action and NOT the barrel. The thread morphed into barrel wear somewhere along the line, but that was never part of the test or the statement on reliability, or sustained fire.

 

Don't recall any mention of shotgun life expectancy here. Do shotguns last longer because of less gas/friction, become less accurate with use? ....Do tracer rounds cause more wear?

 

Formerjughead, I stand by my statement that you can shoot out a barrel especially in Magnums without having improperly maintained the firearm and call your attention to this discussion of a few shooters that spend some time dealing with this phenomena: Barrel life (Bart Bobbitt)
It can simply be done by using an erosive powder and the extra power of the magnums increases exponentially the erosion of the barrel----of course it must be said that you may continue to use the gun but it may not have a desirable performance if you are trying to take off prairie-dog heads at excess yardage. I will also say there are erosive powders still manufactured because they work well when applied to more moderate loads in cartridges. I will also say that a person told me about heating up his barrel until it fired on its own because he was in a combat situation and was more concerned with handling a threat than with proper "rest" time for his weapon. I will concede I am no expert but I have done some reading and some shooting, maybe a lot of shooting and I generally love the regular powered cartridges that deliver long life if you do maintain your guns well. Not trying to establish any wild claims or even full knowledge of guns....there are many who daily here demonstrate more knowledge than I. I will say I do love to take military guns to the range and shoot against the high dollar versions and they often beat me but not always.

 

You keep saying this but it's clear that one of the reasons for water cooled guns was to allow longer continuous fire. You've done nothing to substantiate your claims as to regards to water cooled machine guns.

Indeed but you've questioned the story based on barrel life. Furthermore the document I produced suggested barrel life approaching those values is possible. It also indicated that there were a number of ways to determine if a barrel had exceeded it's life and mentioned that even one that was worn was not necessarily useless. Part of the problem is you seem to be ignoring just why long bursts can be detrimental to the life of the barrel.