Gun's barrel life prediction

[Perfectionist]

What all methods are used to predict the life of gun's barrel in terms of EFC?

[dimreepr]

What is EFC? It's not mentioned here.

[Ophiolite]

Effective Fire Control? That's a WAG! Presumably one can reach a point where the gun is still capable of firing, but range (because of partial gas bypass) and azimuth (because of minscule deviation) are compromised.

[Prometheus]

I've no idea about guns or even what an EFC is, but the lifetime of machine parts is often modelled by some kind of Poisson process or survival analysis.

[StringJunky]

 

 

Effective full charge[edit]

(Note: The British Army term is usually equivalent full charge)

Gun barrels naturally experience internal wear when fired, caused by mechanical wear from the projectile moving along the barrel, and thermal and chemical wear from propellant gases. This wear can reduce muzzle velocity and hence range, affect accuracy, produce unstable projectile flight, and, eventually, cause the gun barrel to fail.

Most guns are capable of firing different types of ammunition with varying charges, and not all of these combinations produce the same firing damage per round fired. The concept of ‘effective full charge’ provides a means of estimating the remaining life of a gun barrel taking into account the varying charges that can be fired from it before it becomes so worn as to be unusable, or no longer safe.[15]

To illustrate, the round (i.e. the combination of projectile and propelling charge) that produces the most firing damage is assigned an effective full charge (EFC) value of “one”. Other round combinations are assigned lesser values derived from testing and experience.

If a gun barrel is capable of firing three different round types: round A (EFC = 1); round B (EFC = 0.75); and round C (EFC = 0.25), and if 100 of each round type is fired, then the barrel is said to have fired (100*1.00) + (100*0.75) + (100*0.25) = 200 EFCs.

If it had previously been determined from testing and experience that this type of barrel has an estimated wear life of 250 EFCs, this specific barrel is at about 80% of its useful life. Plans would be made to order a replacement barrel within the time an additional 50 EFCs were expected to be fired. However the actual decision to retire any specific barrel would be made on examination and measurement of actual wear rather than that predicted by the EFC count.[15]

In practice a barrel might be replaced before reaching its EFC life, or the limits of wear. In the case of the 15-inch guns fitted to the World War I Marshal Ney-class monitors a gun was generally condemned when wear reached about 0.74 inches at one inch from the start of the rifling. However it was the usual practice to replace guns when their projected remaining life fell below the ship’s normal full outfit of ammunition per gun, which ensured that the entire magazine could be safely fired in action.[16]

https://en.wikipedia.org/wiki/Glossary_of_British_ordnance_terms#Effective_full_charge

[Ophiolite]

Nice one.

 

(Useful for me, since I just started a brief study of World War II artillery practices, unit organisation and engagements. Like most specialties it is replete with abbreviations, though I had not run across this one.)

[StringJunky]

Nice one.

 

(Useful for me, since I just started a brief study of World War II artillery practices, unit organisation and engagements. Like most specialties it is replete with abbreviations, though I had not run across this one.)

You were on the right track.

[Perfectionist]

 

 

 

Effective full charge[edit]

(Note: The British Army term is usually equivalent full charge)

Gun barrels naturally experience internal wear when fired, caused by mechanical wear from the projectile moving along the barrel, and thermal and chemical wear from propellant gases. This wear can reduce muzzle velocity and hence range, affect accuracy, produce unstable projectile flight, and, eventually, cause the gun barrel to fail.

Most guns are capable of firing different types of ammunition with varying charges, and not all of these combinations produce the same firing damage per round fired. The concept of ‘effective full charge’ provides a means of estimating the remaining life of a gun barrel taking into account the varying charges that can be fired from it before it becomes so worn as to be unusable, or no longer safe.[15]

To illustrate, the round (i.e. the combination of projectile and propelling charge) that produces the most firing damage is assigned an effective full charge (EFC) value of “one”. Other round combinations are assigned lesser values derived from testing and experience.

If a gun barrel is capable of firing three different round types: round A (EFC = 1); round B (EFC = 0.75); and round C (EFC = 0.25), and if 100 of each round type is fired, then the barrel is said to have fired (100*1.00) + (100*0.75) + (100*0.25) = 200 EFCs.

If it had previously been determined from testing and experience that this type of barrel has an estimated wear life of 250 EFCs, this specific barrel is at about 80% of its useful life. Plans would be made to order a replacement barrel within the time an additional 50 EFCs were expected to be fired. However the actual decision to retire any specific barrel would be made on examination and measurement of actual wear rather than that predicted by the EFC count.[15]

In practice a barrel might be replaced before reaching its EFC life, or the limits of wear. In the case of the 15-inch guns fitted to the World War I Marshal Ney-class monitors a gun was generally condemned when wear reached about 0.74 inches at one inch from the start of the rifling. However it was the usual practice to replace guns when their projected remaining life fell below the ship’s normal full outfit of ammunition per gun, which ensured that the entire magazine could be safely fired in action.[16]

https://en.wikipedia.org/wiki/Glossary_of_British_ordnance_terms#Effective_full_charge

 

yeah u are very much right.. actually i want to know the methods how the EFC is ascertained for a gun that it will last for 250 EFC for example as u quoted. by what methods manufacturer estimates and predicts life of gun in terms of EFC.? like one could be that thy make one prototype nd fire numbr of EFC rounds? or they carryout modelling and simulations to establish the life in EFC??

[StringJunky]

I found this article that has an Excel download that apparently predicts barrel life: http://www.accurateshooter.com/technical-articles/excel-formula-predicts-useful-barrel-life/ Note the caveat at the end.

[Perfectionist]

Thanks a lot. your input has been very helpful

[StringJunky]

Thanks a lot. your input has been very helpful

That's ok. It might not give you exactly what you want but could be a springboard to the information you want with learning the right terminology for that field. Checking definitions of terms can be a useful way of exploring an unfamiliar field. That's what I did here. If you can find terms or lingo that are unique to that field, enter them in your search terms you can zone in much quicker on your target.

Edited January 16, 2017 by StringJunky

[Perfectionist]

what are the methods to verify a guns EFC life withour firing it for inspection purposes lets say.? if a manufacturer claims that his gun has life of 1500 EFC then how can it be verified.?

[StringJunky]

what are the methods to verify a guns EFC life withour firing it for inspection purposes lets say.? if a manufacturer claims that his gun has life of 1500 EFC then how can it be verified.?

If someone makes a claim then ask them about how they came to that conclusion. They probably empirically tested samples then, based on their testing, they expect their guns to last x number of rounds.

[Bender]

Usually life time comes with a probability: e.g. 95% of the samples will last that long. I don't know about guns.

[StringJunky]

Usually life time comes with a probability: e.g. 95% of the samples will last that long. I don't know about guns.

Yeah, that's what I expect they would say if you asked them.

[Perfectionist]

means there is no short cut empirical formula or other method to verify a company claim of certain EFC rd life? we have to believe whatever the company claims?

[StringJunky]

means there is no short cut empirical formula or other method to verify a company claim of certain EFC rd life? we have to believe whatever the company claims?

How would you know without testing? You need to actually test to get the data to use a formula to calculate EFC; this applies to anything. If in doubt ask the manufacturer for the test data for the model you are interested in or some external tester that does this

[Bender]

I don't know if guns come with a warranty, which guarantees a certain life time. I guess that is difficult, because you cannot prove to have fired a certain amount of bullets.

 

For other products, there are consumer organisations or magazines that test different products and compare them with their specs. I guess they should exist for guns in the US too.

 

Then there is the market effect: if the barrels consistently last less long than the manufacturers claim, nobody is going to buy their stuff. You can look for reviews of other customers. Given the popularity of guns in the US, I expect a lot of info can be found online and in magazines. The main trick is discerning which information is coloured by marketing.

[RiceAWay]

It has to do with the coefficient of the friction of both the barrel and bullet. The rifling, the time in the barrel and the speed of repeating, meaning that how hot the barrel grows and stays. At one point the repeating actions finds a balance between how fast it can grow with the heat it receives from the time in the barrel, the heat absorbed and that radiated including the time if requires to reload an fire again.

 

In other words - it depends.

[Ophiolite]

It has to do with the coefficient of the friction of both the barrel and bullet. The rifling, the time in the barrel and the speed of repeating, meaning that how hot the barrel grows and stays. At one point the repeating actions finds a balance between how fast it can grow with the heat it receives from the time in the barrel, the heat absorbed and that radiated including the time if requires to reload an fire again.

 

In other words - it depends.

And the size of the charge if we are discussing artillery guns.