Firecracking vs Barrel Steel

[ShootDots]

I have noticed over time with many, many barrels that "High Intensity" (read that high pressure / overbore) can and do eat up barrels fairly quickly. I have also noticed, "High Intensity" magnums, i.e. 7 SAUMs and "the like", will eat up barrels quickly even using very slow powders. By the same token, I have seen some magnums shooting fairly stout loads exhibit only very minor wear and that is taking some time to manifest itself!

I am beginning to re-think my "prognosis" of the "main" cause of barrel wear. I am starting to reevaluate the concept of soft or "less than stellar" barrels steels may in fact be the primary cause of short(er) barrel life.. I would appreciate your thoughts on this.. Thanks..

 

[acloco]

Speed and hot barrels.

 

[AJC]

Number on shot strings and single base vise double base powders with high flame temperatures....

 

[Straightshooter1]

It appears to me that it's pressure mostly along with higher temps. How much the chamber expands during firing, then contracting when pressure returns to zero, over and over, along with temps that tend to make the metal a bit weaker for the short period that it's heated up (as in less resistance to the expansion). I like to think of the heat issue analogy as passing my finger through candle flame vs passing it through my annealing torch at the same speed, where one has little effect and the other . . . MUCH more. Bullet velocity/speed has little, if anything, to do with it as the bullet is not moving that fast as it does at the muzzle end where you see little or no firecracking like at the throat end. Though I'm NOT a metallurgist, I've been an airframe mechanic working with metal quite a lot and have some idea how various metal react to pressure and temps. So, this is more MHO than any kind of scientific conclusion. It'd sure be interesting to test this, which is really just a hypothesis, by comparing like chambers, but with them having different expansion properties to see if there might be a measurable difference in firecracking.

 

[mike a]

I have noticed over time with many, many barrels that "High Intensity" (read that high pressure / overbore) can and do eat up barrels fairly quickly. I have also noticed, "High Intensity" magnums, i.e. 7 SAUMs and "the like", will eat up barrels quickly even using very slow powders. By the same token, I have seen some magnums shooting fairly stout loads exhibit only very minor wear and that is taking some time to manifest itself!

I am beginning to re-think my "prognosis" of the "main" cause of barrel wear. I am starting to reevaluate the concept of soft or "less than stellar" barrels steels may in fact be the primary cause of short(er) barrel life.. I would appreciate your thoughts on this.. Thanks..

Thing is how would you know if barrel x is soft and barrel y is hard? In my limited experience it seems to me stainless barrels toast quicker. Mike

 

[ShootDots]

It appears to me that it's pressure mostly along with higher temps. How much the chamber expands during firing, then contracting when pressure returns to zero, over and over, along with temps that tend to make the metal a bit weaker for the short period that it's heated up (as in less resistance to the expansion). I like to think of the heat issue analogy as passing my finger through candle flame vs passing it through my annealing torch at the same speed, where one has little effect and the other . . . MUCH more. Bullet velocity/speed has little, if anything, to do with it as the bullet is not moving that fast as it does at the muzzle end where you see little or no firecracking like at the throat end. Though I'm NOT a metallurgist, I've been an airframe mechanic working with metal quite a lot and have some idea how various metal react to pressure and temps. So, this is more MHO than any kind of scientific conclusion. It'd sure be interesting to test this, which is really just a hypothesis, by comparing like chambers, but with them having different expansion properties to see if there might be a measurable difference in firecracking.

I have had 5 .260A.I.s and most of them last about 1500-1600 rounds. I had one last 2000 and I had another last 1050 rounds. The one with 1050 rounds was in miserable shape with split lands, the edges of the lands broken off and the firecarcking so severe that it literally looked like Alligator hide down about 8" of barrel! I have a .300WSM that has 800 rounds and the firecrackng is so mild that if you did not know what you were looking for, you might miss it! These things puzzle me and it makes me wonder if the softer lots of barrel steel are the real culprit.

 

[riflewoman]

It isn’t pressure (per se), it isn’t velocity. Barrel material has an effect. but... the biggest factor is the amount of powder burnt to the cross-sectional area of the barrel. Expansion ratio is an indicator but a 243 will burn out a 30 inch tube just as fast as as a 22 inch tube.

I have a technical article on this somewhere which gave a huge equation of “best fit “ to some empirical cannon data. But effectively you need to live within the realm of sanity. If you neck down a can of powder your barrel life will be short.

For most rifles this is in the realm of 2600-3400 fps depending on bullet weights. As a guide, take the case capacity of the 30-06 (grains of water) to the bore area of the 30 caliber rifled bore. If you graph the “barrel life” of cartridges to this ratio some trends emerge. The more powder you try to push through a small bore the shorter the barrel life.

 

[ShootDots]

It isn’t pressure (per se), it isn’t velocity. Barrel material has an effect. but... the biggest factor is the amount of powder burnt to the cross-sectional area of the barrel. Expansion ratio is an indicator but a 243 will burn out a 30 inch tube just as fast as as a 22 inch tube.

I have a technical article on this somewhere which gave a huge equation of “best fit “ to some empirical cannon data. But effectively you need to live within the realm of sanity. If you neck down a can of powder your barrel life will be short.

For most rifles this is in the realm of 2600-3400 fps depending on bullet weights. As a guide, take the case capacity of the 30-06 (grains of water) to the bore area of the 30 caliber rifled bore. If you graph the “barrel life” of cartridges to this ratio some trends emerge. The more powder you try to push through a small bore the shorter the barrel life.

I understand the "way overbore" of short barrel life. But with the same cartridges and the same "everything", why do some barrels get about 30-40 percent less life?

 

[Murray Brook]

As you alluded to ,you would think that the quality of the barrel steel would certainly play a part in the life of a barrel.

 

[pdhntr]

I have noticed over time with many, many barrels that "High Intensity" (read that high pressure / overbore) can and do eat up barrels fairly quickly. I have also noticed, "High Intensity" magnums, i.e. 7 SAUMs and "the like", will eat up barrels quickly even using very slow powders. By the same token, I have seen some magnums shooting fairly stout loads exhibit only very minor wear and that is taking some time to manifest itself!

I am beginning to re-think my "prognosis" of the "main" cause of barrel wear. I am starting to reevaluate the concept of soft or "less than stellar" barrels steels may in fact be the primary cause of short(er) barrel life.. I would appreciate your thoughts on this.. Thanks..

This is interesting in that I was thinking of doing a comparison this next summer using two different 22-250 barrels. I have a lot of experience with the causes of shot out barrels. And I just rebarreled with "one" brand of barrel and am thinking of building another 22-250 and using a different manufacturer for the barrel. Both twists would be the same as would length and loads used.

The reason I was going to try this is that I am seeing more wear in this barrel than I have seen in others that I have used. I don't have a clue if the different manufacturers use different recipes for their steel or not.

I would be interested in Stan Taylors (I believe?) opinion on that. I think he might know.

Problem is, a report of findings could get me kicked off the forum. Don't really want to do that.

Jim

 

[riflewoman]

The US Army has tested different barrel materials against erosion for several decades now. From tool steels to even some exotics. There are a dozen or so reports out there, most of which are unclassified, basically all reaching the same conclusion. That for high volume production, the best approach is to chromeplate the barrel, at least the first 6 inches. Plated barrels like this are seldom stellar accuracy barrels. This is why the M14 NM barrels were not chrome plated.

For machine guns the best way was to freeze-Shrinking a Stellite liner into the barrel. Stellite, being a Cobalt Nickle Alloy, has the harness and toughness and flame resistance to stand up to long bursts of belted ammo. M60 barrels had Stellite liners, at least for a while.

Some materials resist the erosion of the powder gases but they can be wetted by the liquid gilding metal from the bullet. Yes, the bullets literally melt from friction. At least the skin of the jacket. This wetting then causes small chunks of the barrel to be literally ripped from the base metal and carried out by the bullet. Bad Juju.

 

[ShootDots]

The US Army has tested different barrel materials against erosion for several decades now. From tool steels to even some exotics. There are a dozen or so reports out there, most of which are unclassified, basically all reaching the same conclusion. That for high volume production, the best approach is to chromeplate the barrel, at least the first 6 inches. Plated barrels like this are seldom stellar accuracy barrels. This is why the M14 NM barrels were not chrome plated.

For machine guns the best way was to freeze-Shrinking a Stellite liner into the barrel. Stellite, being a Cobalt Nickle Alloy, has the harness and toughness and flame resistance to stand up to long bursts of belted ammo. M60 barrels had Stellite liners, at least for a while.

Some materials resist the erosion of the powder gases but they can be wetted by the liquid gilding metal from the bullet. Yes, the bullets literally melt from friction. At least the skin of the jacket. This wetting then causes small chunks of the barrel to be literally ripped from the base metal and carried out by the bullet. Bad Juju.

That "melting of the skin of the jacket" must have been the reason for one of my 260A.I. extremely short barrel life. Still the question remains as to WHY that barrel's life was so short, when others were considerably longer under nearly identical circumstances.

 

[Straightshooter1]

There ARE differences between various steel, depending on the manufacturing process and what the objective is for the steel and how it's intended to be used. Some steel is more brittle than others and some are way more soft or stronger and much in-between. So, I have little doubt that the "quality" of a barrel's steel is a big factor . . . as is the particular spec variations of barrels for a particular caliber.

 

[riflewoman]

That "melting of the skin of the jacket" must have been the reason for one of my 260A.I. extremely short barrel life. Still the question remains as to WHY that barrel's life was so short, when others were considerably longer under nearly identical circumstances.

Perhaps, but IMO the lowest limit for the “308” case barrel life wise is the 7mm-08. For the 6.5 mm the largest case capacity IMO is between the Grendel and the Creedmoor. For 6mm it is the Grendel or 6-250. Larger bores are all getting in to magnum sized cases and recoil becomes punishing so barrel life becomes largely academic.

 

[riflewoman]

I might quibble with “900” defining “overbore” but this article is very much on the right track.

https://www.accurateshooter.com/technical-articles/overbore-cartridges-defined-by-formula/

 

[Dusty Stevens]

A 7mm short magnum or 7mm rem magnum lasts way less than a 300 short mag or 300 win mag which lasts about half or less as long as a 375 h&h. Doesnt matter the barrel steel (to a point) its the cartridge. A 264 win mag or a 7 stw may last only a few hundred rounds where a 308 may last 5000 and a 22rf may last 80,000 with the same lot of steel. Its the cartridge.

 

[ShootDots]

I might quibble with “900” defining “overbore” but this article is very much on the right track.

https://www.accurateshooter.com/technical-articles/overbore-cartridges-defined-by-formula/

I have read this article a few times. It is excellent..

 

[Dud]

I agree that that overbore ratio is a good predictor but rate of fire and cleaning also have big effects.

When you look at the steel, alloys have allowable ranges, not strict percentages so lots can be fairly different and different manufacturers will heat treat barrels differently.

The rifling profile, twist and button vs. cut rifling also must have an effect.

Then there is use, strings of relatively rapid fire are going to cook a barrel pretty fast and a thin, hunting profile barrel will probably accelerate that because it's missing the heat sink mass of a heavy barrel profile.

There are just lots of variables and I would say that hardness isn't a good indicator of wear resistance because every bullet fired probably creates temperatures close to the annealing temperature of the metal for a short time so hardness probably isn't consistent from one shooting session to the next.

I have heard that Lothar Walther barrels are harder than most others. I would like to try one for that reason but I don't know if that will enhance my barrel life.

 

[LC Tikka]

Do barrels suffer from cavitation burn as happens on marine propeller blades.
L

 

[LA50SHOOTER]

I believe that (but not entirely limited to) steel Quality Does / Is a factor in not only barrel life but accuracy as well.
The barrel makers are the ones who determine if the steel stock that they purchase is in fact acceptable for use. - They can either accept or reject it based on the metallurgical reports on the batch of steel that are available and obtainable to them.

You can bet that if a barrel maker has a u.S. Government contract, which in fact will have stipulations regarding not only accuracy but as well wearability (how much wear is considered allowable during an endurance test and then still be able to produce a predetermined acceptable level of accuracy) that they (the barrel maker under contract) will be looking very closely at the metallurgical reports for the steel prior to acceptance.
I base my statement off of actual conversations with owners of barrel making companies.

Barrel making is a business that is driven by factors such as raw product availability (barrel steel) and waiting time, current market demand, (how many customers do we have) and the ability to satisfy those customers and keep them happy. As well, there are more custom barrel makers today than there have been in the past so the market in itself has evolved and the number of shooters using custom barrels has also increased over time.

This is my .02 based on the +65 barrels that I’ve ordered since 2008.

- Ron -