Barrel Materials

I dropped a barrel erosion gage down an M2 50 barrel and it actually protruded out the front of the barrel about an inch. The gages are about 8" long, slightly tapered, with rings cut into the gage at varying thicknesses along the gage. It should never have gone past the KNURLED handle. I have seen M2, M85, and M60 barrels with huge areas in front of the chamber missing lands. Just plain gone. Sooo, maybe the absorbing of carbon into the lands is causing the erosion. The use of stellite liners in about the first 8"-10" of the 50 barrels helped stop some of that erosion problem. As for hammer forging 4100 series steel, just what hardness do you start out at? Barrel steel is commonly 26-28 RC before drilling and rifling. I believe there was an Austrian company doing hammer forging on high power barrels a few years back, but it does not seem a common practice.
 
The first hammer forged barrels I know of for sure were from Steyr. They just polished the hammer marks but left the pattern so you would know how the barrel was made.
I am fairly sure H&K hammer forges centerfires and has for years.

I recall reading that Ruger had a hammer forge machine parked in the plant for some time before they decided they could make their own cheaper than they could buy them.

Remington reportedly went from button to hammer forge a while back. Even Winchester in their last years in New Haven had gone to hammer forge. One article said their Model 70 target was unusual in having a 4 groove hammer forged barrel.
 
I wish I had a copy of the original report. It demonstrated that it was NOT 'erosion' [wearing away] . The way to minimize it is to keep things cool ! NO rapid fire ! This keeps temperatures down reducing the absorbtion of carbon by the steel by the steel .The term 'Erosion' has been misused for so long shooters refuse to consider any other term.Doesn't anyone on this forum know of the report I'm talking of ?? It's been around for many years .
 
Let me ask you folks a question. Having shot benchrest rifle for some years it seems to me that how a barrel "breaks in" is important. A new barrel will hold more copper on fewer shots than a broke in barrel. You reach a sweet spot in the short life of a bench rest barrel where it almost stops retaining copper. Is that a possible reason for SS over CS?
 
mete,

What you are talking about in terms of carbon uptake by barrel steel leading to heat checking and cracking is what everyone else in the thread is calling "erosion."

Because that is what it is. Steel uptake of carbon creates a very brittle crystalline "flake" which is then detached and blown away by subsequent rounds down the tube.

Whether you classify that at chemical erosion, thermal erosion, or physical erosion doesn't really matter, there is no way to completely avoid the truth that every round down the tube is going to wear at it a little bit more.

Jimro
 
Whole lot of hammer forging going on. I can see I have been out of it too long. I was talking to a friend the other day and we were discussing how we toss around the saying "About twenty years ago...." . We have decided to say 30 years now.
 
I thought that 'mete' set it pretty much straight in defining the types of erosion on the link that was posted.

Anyone who has used a grinder can tell you that heat exacerbates metal wear. But I thought that it's funny people still continue to contribute after that post.

Apparently, it's both; carbon and physical degradation, that contribute to bore wears, heat just exacerbates things!

I thought it was primarily physical erosion that caused a bore to degrade, thanks for all the good posts!!

Edit --- here's the link again: http://precisionrifleblog.com/2012/07/09/practical-tips-to-extend-barrel-life/

2nd edit: mete doesn't seen to accecpted that multiple factors are involved in barrel wear, just as I was focused on 1 cause.
 
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Some think I'm too technically precise. The hot gases contain carbon which is absorbed by the steel - changing the alloy. That alloy is brittle causing cracking and spalling of the steel .Oops, another big word :rolleyes:.Spalling is not wear. But since 'wear 'is engraved in your minds lets leave it at that .:)
 
Spalling is part of the issue, although the term spalling itself has nothing to do with carbon absorption as it describes a purely physical phenomena. Mechanical erosion is another, as the "sandblasting" effect of unburnt, partially burning, and carbon residues are blasted against the steel by the forces of ignition.

Whatever the cause, the end result is less steel than there was before. Generally that is referred to as erosion.

Jimro
 
The reason that Mete's point of clarification is important is this... If the erosion process is purely physical (particle impact etc), then the only barrel parameters that matter are physical properties, such as hardness. If however, there is a chemical reaction aspect to the observed erosion, it means that the barrel chemistry could play a role. For instance, if some steels are less likely to absorb carbon from a hot gas, they will be less effected, all else being equal.
 
btmj,

Everything in firearm design is a trade off. Even hard coated steel barrels experience erosion. I've seen enough hard chrome military barrels rejected because of exessive throat wear to understand that hard chrome gets worn away too, and it doesn't have a carbon uptake problem. Double chrome SAW barrels wear out too, and since you eliminate "carbon uptake making steel brittle" because there is no exposed steel, only the hard chrome, you are left with mechanical erosion.

Jimro
 
Thanks

Thanks for all the input.
The post started off slow then got going.... Lots of knowledgeable folks out there.
 
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