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Discussion Starter · #1 ·
I've been finding it difficult to explain to a few the process and effects of bore erosion.

They don't seem to realize that Gas erosion can "wash" both lands and grooves equaly so to the eye the bore doesn't look worn but has become oversized. A star gauge could spot the difference but not the naked eye.
The definition of servicable barrel life and usable accuracy also seems to escape them.

If a rifle can not deliver its rounds on target at a specified range using the issue sights and range settings it doesn't matter what the group size is. as far as the military is concerned that bore would be considered worn out. "Maggie's drawers" is the term I believe.
Blowby reducing velocity and screwing up harmonics, or mutilating bullet jackets by overheating.

I've seen barrels lose chunks of land at mid bore due to gas cutting of craze cracking, which some seem to believe does not exist.

So if anyone knows of a good online source that can explain gas erosion and craze cracking in simple terms hopefully with illustrations that would be of great help.

The difference in gas erosion between various types of propellant according to burning time is another thing.

The net seems to have next to nothing on ballistics for some reason.

I guess they've thrown the baby out with the bath water by removing some information.

Any links will be of help since I can at least look for keywords or links to other sites.

And if anyone posts a misunderstood quote from Peter Laidler they'd be wasting my time and theirs.
 

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Discussion Starter · #3 ·
That might help a bit, I'd already posted information on naval guns but no one seems to have gotten the connection between cracking and gas erosion or the differences between mechanical erosion and gas erosion from those sources.

The terminology though should help with key word searches.

I did have dozens of specialized search engines for this sort of thing but my old PC overheated and all that stuff is lost.
 

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I'll keep searching to see if I can find something to help you. I understand what you are looking for. Many years ago when I was studying gunsmithing, I remember reading articles on barrel erosion. Much of the data concerned early double-based powders(nitrocellulose and nitroglycerin). The higher the nitroglycerin the more erosion due to higher combustion temperatures(the Swedes had this problem with early 6.5 ammo). Single-based powders(nitrocellulose) that burn longer at lower temps exhibit less erosion( ex. IMR series). One text mentioned "scaling", which was described surface cracking of the barrel steel and subsequent peeling of very thin layers of steel from the bore. I actually have a 1916 Spanish Mauser that has this issue. The bore is "hairy" and snags patch fibers when you clean it.
 

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Discussion Starter · #5 ·
I'll keep searching to see if I can find something to help you. I understand what you are looking for. Many years ago when I was studying gunsmithing, I remember reading articles on barrel erosion. Much of the data concerned early double-based powders(nitrocellulose and nitroglycerin). The higher the nitroglycerin the more erosion due to higher combustion temperatures(the Swedes had this problem with early 6.5 ammo). Single-based powders(nitrocellulose) that burn longer at lower temps exhibit less erosion( ex. IMR series). One text mentioned "scaling", which was described surface cracking of the barrel steel and subsequent peeling of very thin layers of steel from the bore. I actually have a 1916 Spanish Mauser that has this issue. The bore is "hairy" and snags patch fibers when you clean it.
Finally someone that understands what I'm talking about.

One problem is that trying to explain this sort of erosion patter in simplified terms gives people visions of yosemite sam type cartoons. Though some of the stuff that happens to a barrel during its vibrations actually resembles the cartons much with movements of less than one thousandth of an inch.

Some of the older Mausers got exposed to cordite like powders early on, as much from home brewed stuff from dynamite factories as from the real deal.

The real danger is when the erosion removes material from lands and grooves equaly, then it can't be spotted by just looking down the bore. depending on the propellant there can be sections near the throat only a few thousandths oversize and then a smoothly curved section where the bore looks normal but is so eroded that the bullet isn't even contacting the lands most of the way, then it hits the relatively un worn section about two thirds of the way up.
The jacket by this time is gas cut and hot as a welding rod, the core softened or partly melted. Cordite burns so much hotter that the effects are greatly increased.
Just before the propellant reaches its final burn the gases swirl and eddy changing the pattern it cuts into the steel.
Probably a good thing some of these older bores have the rifling worn out near the muzzle by steel cleaning rods, that at least cuts down on resistence a bit.

I remember that some earlier model .303 rifles had the last one third of the bore lapped out several thousandths over size so they could be used in emergencies. I always wondered how they expected that to reduce pressures and stress on the action, This may be why.
 

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There's probably not much data online because the problem pretty much disappeared before the internet appeared.

Aside from wrecking crowns by excessive careless use of cleaning rods the only problems I've seen in any post WWII rifles has been from throat erosion, corrosion due to neglect - and that usually appears on the exterior, too, and just plain wearing out due to lots of shooting.

The worst cases of throat erosion were in some rifles at an estate auction sale. The deceased was a Weatherby fan, had several in Weatherby magnum chamberings, a rifle range in his backyard, and I was told he shot them every day! The bores were mirror bright, but at least the first 4 inches in front of the chambers loked strange - melted! Kind of like a Dali painting of a rifle bore. Gas erosion from the hot magnum factory rounds had burned its way up the barrel. If it showed up in reduced accuracy I wonder why he kept shooting them without rebarreling? And how could his shoulder stand it? I've got a Weatherby Vanguard in 300 Wby magnum and you DO NOT want to shoot it every day! Even with a properly fitted stock it's not comfortable.

In more mild target rounds, in my experience, the barrel wears out first after many thousands of rounds, the edges of the lands rounding.
 

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Discussion Starter · #7 ·
There's probably not much data online because the problem pretty much disappeared before the internet appeared.

Aside from wrecking crowns by excessive careless use of cleaning rods the only problems I've seen in any post WWII rifles has been from throat erosion, corrosion due to neglect - and that usually appears on the exterior, too, and just plain wearing out due to lots of shooting.

The worst cases of throat erosion were in some rifles at an estate auction sale. The deceased was a Weatherby fan, had several in Weatherby magnum chamberings, a rifle range in his backyard, and I was told he shot them every day! The bores were mirror bright, but at least the first 4 inches in front of the chambers loked strange - melted! Kind of like a Dali painting of a rifle bore. Gas erosion from the hot magnum factory rounds had burned its way up the barrel. If it showed up in reduced accuracy I wonder why he kept shooting them without rebarreling? And how could his shoulder stand it? I've got a Weatherby Vanguard in 300 Wby magnum and you DO NOT want to shoot it every day! Even with a properly fitted stock it's not comfortable.

In more mild target rounds, in my experience, the barrel wears out first after many thousands of rounds, the edges of the lands rounding.
Worst case I've seen was a Lithgow from an old collection. A friend brought it over to see if I thought the bore would clean up well enough to shoot. It had a chunk of land missing just above mid bore.

The number of rifles showing up these days that were first bought off the civilian market after decades in service in third world countries then fired thousands of rounds of the worst quality ammunition and never properly inspected is the real problem. Wasn't uncommon here for guys to plink with a WW2 rifle same as with a .22 rf, ammo, especially the lowest quality, was dirt cheap back then, as little as $3 per one hundred rounds or even less.

Saw a 1912 BSA No.1 recently and the lands seemed abnormally tall and almost peaked in appearance. I'd been wondering what might cause that.
Could be the erosion had cut away the bottom of the grooves faster than the lands. perhaps the type of jacket material used for most rounds fired through the bore built up thick on the lands.

Someone posted images of an enfield bore recently that looked like the cargo hold of the Spaceship in the film "Alien". Thats pretty badly worn.

A handload balanced for the individual rifle can keep even a nearly worn out bore in the running for awhile longer, but not necessarily safely.

A lot of No.4 rifles that won't handle boatail bullets have been showing up, and thats a sign that throat erosion is well underway.
 
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