Decrease throat erosion with longer barrels?

[TracySes23]

If you are trying to reduce throat erosion, then melonite the barrel. Cost is $100 and way longer barrel life

I did a small amount of research concerning melonite on barrels. I thought I read something about using this process on stainless steel that might be a problem.
I know for fact when you begin mixing carbon with stainless steel it takes away the qualities of stainless steel. In the past, I've had a few lengthy conversation with metallurgists at Carpenter Steel. Carbon always induces magnetic qualities in stainless steel. Not to say it becomes magnet, but a magnet will be attracted to it. Carbon also can begin to reduce it's resistance to rust.
The description I read indicated the melonite process infuses nitrogen & carbon into the metal.
As a machine shop supervisor in a research facility at the University of Illinois, I learned there aren't very many surface treatments that don't add at least some thickness to a surface. I didn't look into this process long enough to know it that's true or not. I saved a couple of bookmarks to remind me to look into it more.

 

[Michael Eichele]

FYI, magnets will stick to a stainless steel rifle barrel normally.

 

[shortgrass]

I first investigated the melonite/black nitride process because it was recommended by several bench rest shooters I know and trust. If it effected accuracy, they'd want nothing to do with it. S.S. barrels, in general, are made of 416R. It is already magnetic! As for corrosion,,, I've personally not seen it in any barrel I've had treated. Of course, I'm very diligent about cleaning after every shooting session, be it a single shot at a coyote or 60 at the range. After a year and a half of using barrels that have been treated, I have absolutely no complaints. It preforms as advertised. This subject has been explored, in depth, on this forum and several others in the past.

 

[TracySes23]

FYI, magnets will stick to a stainless steel rifle barrel normally.

Thanks for the info, I didn't know that. All knowledge is useful.

In the area of research where I worked (University of IL), if it had carbon in it, it wasn't considered a true stainless steel. Some professors can get a little thin skinned if you question them about this. There's problems in "Electron Beam Microscopes" and stainless steel which has carbon in it. It causes an electron beam to stray places they don't want it to go.

 

[TracySes23]

I first investigated the melonite/black nitride process because it was recommended by several bench rest shooters I know and trust. If it effected accuracy, they'd want nothing to do with it. S.S. barrels, in general, are made of 416R. It is already magnetic! As for corrosion,,, I've personally not seen it in any barrel I've had treated. Of course, I'm vey diligent about cleaning after every shooting session, be it a single shot at a coyote or 60 at the range. After a year and a half of using barrels that have been treated, I have absolutely no complaints. It preforms as advertised. This subject has been explored, in depth, on this forum and several others in the past.

Thank you sir for your input. I'll put melonite on my list of things I want to research here on this website.

 

[Catfur]

I know for fact when you begin mixing carbon with stainless steel it takes away the qualities of stainless steel. In the past, I've had a few lengthy conversation with metallurgists at Carpenter Steel. Carbon always induces magnetic qualities in stainless steel. Not to say it becomes magnet, but a magnet will be attracted to it. Carbon also can begin to reduce it's resistance to rust.
The description I read indicated the melonite process infuses nitrogen & carbon into the metal.

FYI, magnets will stick to a stainless steel rifle barrel normally.

There are many types/grades of stainless steel. Broadly (very) speaking they can be divided into types based on what sort of crystal the iron in them forms, austenitic or ferritic. Austenite forms in plain iron at high temperatures, but is stabilized in low (read normal) temps in certain stainless steels, it is non-magnetic. Ferrite is the crystal form in room temperature iron, and certain other stainless steels, it is magnetic. Rifle barrels are typically made from a ferritic stainless steel, stuff like stainless steel food service equipment is typically made from austenitic stainless.

Infusing carbon into an austenitic stainless steel can cause a phase change into ferrite. Infusing carbon into a ferritic stainless steel will not (it's already ferrite). Infusing carbon into any stainless steel can cause the chromium in solid solution to precipitate out into chromium carbide crystals, depending on the temperature that the process is carried out at. Precipitating out the chromium will decrease the corrosion resistance of the steel. The nitrogen infused in the ferritic nitrocarburization process will increase the corrosion resistance of the steel.

Net result is (typically), for a Melonited stainless barrel, better corrosion resistance than carbon steel, less than some grades of stainless.

 

[Michael Eichele]

I'm not 100% sure so please don't hang me if I'm wrong but I do believe there is a small amount of carbon in 416r SS and quite a bit of chromium. I've heard that true SS is softer than other steels but its the addition of chromium that makes 416r harder.

What I do know is that 416r SS barrels DO rust. Not nearly to the degree other steels and dont pit as bad. Rust also clean off much easier. But good SS does rust and has magnetic properties.

 

[Michael Eichele]

Catgut,

I was typing the above post when you posted yours.

Thank you for the insight. I guess it confirms what little I do know about 416r

 

[TracySes23]

Catgut,

I was typing the above post when you posted yours.

Thank you for the insight. I guess it confirms what little I do know about 416r

I don't know about anyone else, but I'm learning about all kinds of things I never thought to ask about. This is great!!

 

[TracySes23]

Most barrel erosion occurs in two areas of the barrel: the throat and the muzzle. The throat gets the brunt of the abuse through heat and chemical. The muzzles tends to wear and becomes less round and more "fish eye" in shape. As a general rule, bullets will gain about 25 fps for every inch added. But this is only true for barrels in the 20' to 26" range. After that, it becomes a game of diminishing returns. It can actually become a detriment and slow the bullet down if the barrel is too long. Dan Lilja wrote a pretty interesting article on the subject a while back:

Lilja Precision Rifle Barrels - Articles: Barrel Lenghts and Velocities in the 338/378 Weatherby Magnum

My point is this: you need substantial drops in powder to begin to realize any saving in the area of throat erosion. Even the 30-06 burns 18% more powder, but does not suffer from shorter life due to barrel erosion. Most starting loads in reloading manuals for any of the above calibers are only 5% under the listed max loads. To gain any appreciable decrease in barrel wear (such as between the .308 and the 300 Win Mag), you are looking at a decrease in powder of 30% or more. It just isn't practical in light of other factors mentioned previously.

That was very interesting reading. I noticed a pattern in the different bullet weights.
The lighter bullet reached a maximum velocity at a shorter barrel length than heavier bullets did. The 250 gr reached maximum velocity with the 42 inch barrel. It appears as though the remaining energy left at that length wasn't to increase velocity beyond the 42" length.
Then for the 300 gr bullet, remaining energy maxed out in the 46 inch barrel length.
Although the data is less complete it suggests the 320 gr bullet also maxes out in the 46 inch barrel length.
This seems to suggest the lighter bullets have less remaining barrel length left to be slowed down by friction.
Before I read this, I would have guessed the opposite would be true.

Thanks for the link!

 

[shortgrass]

I'm not 100% sure so please don't hang me if I'm wrong but I do believe there is a small amount of carbon in 416r SS and quite a bit of chromium. I've heard that true SS is softer than other steels but its the addition of chromium that makes 416r harder.

What I do know is that 416r SS barrels DO rust. Not nearly to the degree other steels and dont pit as bad. Rust also clean off much easier. But good SS does rust and has magnetic properties.

Yes, 416R has carbon. Barrel steel is heat treated (hardened and then tempered). It wouldn't last long, otherwise! http://crucibleservice.com/eselector

 

[Lefty7mmstw]

Not to digress too far on this but I was thinking of the 204 ruger when I perused this thread. When the specs on this round came out I was surprised on them only running the M.A.P. at 57 kpsi instead of 65 kpsi like virtually all other modern bolt action chamberings. It turns out that dropping the pressure to where they did helped the bore life out immensely. They also were using a copper scrubbing powder by primex in the initial loadings, but that's only why they weren't fouling quite as badly ( though excessive fouling can hurt bbl. life).
By running a slow enough powder that you only push up to 55-60 kpsi and using a slightly longer barrel to compensate for it you could see longer longer barrel life. By limiting rate of fire and bbl heat combined with sensible loads you would probably actually see greater gains in bbl life though.

 

[TracySes23]

Not to digress too far on this but I was thinking of the 204 ruger when I perused this thread. When the specs on this round came out I was surprised on them only running the M.A.P. at 57 kpsi instead of 65 kpsi like virtually all other modern bolt action chamberings. It turns out that dropping the pressure to where they did helped the bore life out immensely. They also were using a copper scrubbing powder by primex in the initial loadings, but that's only why they weren't fouling quite as badly ( though excessive fouling can hurt bbl. life).
By running a slow enough powder that you only push up to 55-60 kpsi and using a slightly longer barrel to compensate for it you could see longer longer barrel life. By limiting rate of fire and bbl heat combined with sensible loads you would probably actually see greater gains in bbl life though.

Your thinking appears to follow my line of thinking from the original post. Although my reasoning came from a different direction, lower pressure would've been the result of my thinking also.

Personally, I think I'd rather stay away from any abrasive compounds for cleaning a barrel. Since I discovered Wipe-Out foaming bore cleaner about a year ago, I'm gonna stick with that unless I see a reason to change. I believe using abrasives takes a technique that needs to be learned to do it well. I prefer using a method that won't ruin a barrel, simply because I don't know what I'm doing with abrasives on a barrel.
Contrary to what most people think, there are a few soft metals that have abrasive qualities. Copper is one of them. It will wear out Hi-Speed cutting tools much faster than you might expect. These tools have an approximate hardness of Rockwell 68 on the C scale. Much harder than barrel steel. Aluminum alloys with a higher than average Silicon content will do the same. Perhaps I'm wrong, but as long as copper fouling is removed when necessary, I think copper jacketed bullets will break in a barrel quite well.

 

[LDHunter]

Something else to consider and this is pretty self evident is that the bigger the charge and the smaller the caliber (internal diameter) of the barrel, the faster you'll have throat erosion. With a cartridge like the 22-250 you're pushing a lot of hot burning powder down a relatively small hole and that also increases throat erosion.

Using pressure as a guage is a good rule of thumb but there are many more factors.

How about the fact that a 30 caliber bullet needs less powder to get it up to speed and has a larger "hole" for that all that burning powder to crowd through than a 243 shooting the same weight bullet needs. In this case it's about the efficiency of larger base of the 30 caliber bullet being acted on by the pressure of the burning powder vs the relative inefficiency of the 243 caliber bullet with the smaller diameter for the powder to push against.

I've had 308's fire virtually thousands of medium pressure loads show almost NO barrel throat erosion while a 243 at the same pressure shows a lot more and faster.

There are so many factors to consider and all of this is why my high volume shooting is done with cartridges like 223's and 308's. It's not just about the cost of rebarreling but also the time the gunsmith takes to get around to rebarreling for you. LOL

This is a very interesting topic and I'm glad the OP brought it up.

The only two barrels I ever cooked to the point that accuracy was seriously affected was a 22-250 barrel that got really hot shooting in a target rich environment (prairie dogs) and a 30-378 Weatherby that simply showed accuracy degradation after a mere 200 rounds and was never fired hotter than two shots and a complete cooling and I bought that rifle new so I was sure of the round count.

Interestingly enough I shot a few thousand rounds out of a 300 Win Mag Sendero a few years ago and it seemed to get more and more accurate as I shot it more and more. The throat showed a fair amount of erosion but accuracy seemed to be affected only posltively as time went on... Maybe I just got really comfortable shooting it and will never know but rifle would flat out shoot... I guess I sold it... I don't see it around here... LOL

Bob