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this question is for Clay, but anyone else who would like to answer is welcome. you said that a 220 swift is hard on a barrel. h

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  • kyle7735
    replied
    220 swift is such a fast bullet that it is just hard on barrels

    Leave a comment:


  • DakotaMan
    replied
    Great comments guys... a most interesting thread! I just hope I don't have nightmares tonight dreaming about my beautiful barrels eroding to pieces the next time I pull the trigger. Great comments!

    Leave a comment:


  • MLH
    replied
    They ran into an anomaly with flame temps - with certain powders that burned at higher temperatures bore erosion actually decreased. They think a major reason is substantially higher amounts of nitrogen in the gas. Nitriding hardens steel. Hydrogen on the other hand can dissolve into hot steel then reform into hydrogen gas, which embrittles steel causing it to crack.

    Manufacturers include additives to control powder characteristics - no telling what these are but some molecules are likely diffused into the steel where they can form other compounds, or just imbed into the cracks causing stress problems. Oxides are formed to some extent - very brittle and different densities than the bore. There doesn't appear to be much free oxygen so a cutting torch effect wasn't mentioned. Doesn't mean that it doesn't exist.

    They looked at titanium dioxide. That brought erosion down. They suspect that the powder fills the cracks and insulates it from high heat.

    They also didn't evaluate primer combustion products, or copper and zinc from the brass.

    So, the chemistry of the powder can increase or reduce erosion, or both. Nitrogen gas might harden the surface but hot Nitrogen gas blow increases heat transfer and erosion. Like I said they don't understand everything. I think a few people could spend a lifetime trying to figure all this out.

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  • bonnier-admin_2
    replied
    Reaction with the bore?

    What you’re saying is, as a cutting torch actually uses oxidation/instant rusting to cut metal so does the powder with the bore

    Leave a comment:


  • MLH
    replied
    A couple of other points:

    The studies do not take the case and bullet composition or all powder additives into account. More stuff to imbed in and react with the bore. Barrel composition has an effect. As others and Lilja point out, stainless steel barrels are usually more erosion resistant.

    Another thing Lilja found on his barrels – going to 3 grooves, with lands 2x the width of those in 6 groove barrels, reduced barrel erosion significantly. He suspects it might be due to the larger land surface. He doesn’t mention if there are any pressure changes between his 6 and 3 groove barrels.

    Regarding the progressive twist barrels – it seems logical that less twist at the throat would reduce stresses on the lands. I wonder if it also leads to higher sustained pressure down the bore since the lands are continuously pressing different angled grooves into the bullet. If S&W found less bore erosion it seems they would advertise that. By the way, Bartlein makes progressive (gain) twist barrels for rifles. Seems there would be others.

    Then don't forget polygonal rifling - my H&K USP Compact .357Sig had it. Claim was that reduced bore erosion significantly. Complex is an understatement.

    Leave a comment:


  • bonnier-admin_2
    replied
    For hunting, if you can't shoot "MOP" don't take the shot!

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  • bonnier-admin_2
    replied
    By the way, a 30-06 loaded with 110 grain soft points is a real screamer and excellent on critters! Shooting 130’s is my #1 choice for both critters and Mule deer!!!

    Instead of cutting my teeth on 22LR, it was just an ample supply of 30-06 loaded with 130’s 54 grains of IMR4064!

    Leave a comment:


  • bonnier-admin_2
    replied
    WOW MLH that’s pretty good, I’M EMPRESSED NO JOKE, SIR!
    Barrel erosion is a complex interaction of heat, pressure, friction, and chemistry, though, not necessarily in that order.

    It’s noonish somewhere so here is the answer!
    If not cleaning your barrel every 20 rounds, bullet goes from 0 spin to full spinning (running with the lands and groves) within the first couple of inches of the chamber too over heating the barrel then my Competition M1 Garand and especially my Ultra Match M1A should have been toast a long time ago!

    In a nutshell it’s the “ratio of powder/case capacity + duration of burn & velocity of the expanding gas to the caliber/diameter” which acts just like a cutting torch! A properly cared barrel erodes from the throat forward.

    As for Ruger barrels wearing out, the Ruger M77 25-06 lasted a tad bit longer than my Remington 700BDL 22-250.

    I don’t see how anyone other than me should have to worry about burning a barrel out, unless you were out shooting 50 to 100 rounds practically every weekend like I was.

    Leave a comment:


  • MNhunter23
    replied
    very informative thread

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  • MLH
    replied
    Okay, if you want a more thorough explanation: As I said before barrel erosion is a complex interaction of heat, pressure, friction, and chemistry, though, not necessarily in that order. It is not yet fully understood. When you light off a round the powder burns in a very rapid exothermic reaction, basically converting the solid structure of the powder into various other molecules. Some of these are gases, including carbon monoxide, nitrogen, and hydrogen. Water vapor may also be present. The temperature of the burning powder is much higher than the melting point of steel. Luckily, this all occurs in milliseconds so there is very little time to transfer heat to the barrel, case, and bullet (let’s leave lead bullets without gas checks out of the discussion). However, the bore surface is subject to substantial temperature increases.

    In general, the highest heat transfer to the barrel is reached just in front of the cartridge where the hot gases come in contact with the barrel. The case has expanded, sealing off the gases from the chamber. The bullet at this point is accelerating and momentarily slowed when it hits the rifling, creating a pressure spike. The interior of the barrel is pressed outward. . A microscopic layer of the barrel momentarily melts making it more subject to structural changes and mechanical erosion.

    The chemistry of the powder affects erosion. Different combustion products can vary the properties of the steel and its erosion resistance. Molecules from the burning powder are driven into the interstitial layers of the steel, changing its characteristics (including melting point). Nitrogen and hydrogen can further change properties (nitriding actually makes the steel more erosion resistant.).

    If gases blow by the bullet, erosion is multiplied. The expanding gases can move at speeds upwards of 5,000 fps. Turbulent gases substantially increase the heat transfer to the barrel. Throttling of the high velocity hot gases between the bullet and barrel might strip the hot barrel surface. Complex interaction might be an understatement.

    Further down the barrel the temps and pressure are lower and the mechanical effects of the bullet might be more pronounced, but the overall erosion is still much less than at the throat … or at the muzzle … unless you’re using very hard bullets (steel, turned brass, etc). The expanding gases still want to move faster than the bullet. When the bullet just exits the muzzle the gases blow by a very high speed while still under extreme pressure. When the bullet is clear of the muzzle the gases continue to blow out until pressures are equalized. I suspect the wear at the muzzle is a complex interaction similar to that seen at the throat but with lower temperatures and pressures.

    If you look into barrel with a boroscope you might see cracking or crazing (heat checks). This is due to all the above – chemical changes due to interaction of the steel with the powder changes the properties of the surface of the bore – hardness, melting temperature, expansion coefficient, even density. High temps and pressure affect mechanical properties and propagate the cracking. The cracks leave more surface exposed and access deeper into the barrel. These cracks are catch points where material can be mechanically torn off. Differential expansion coefficients between the surface and underlying structure can eventually lead to separation. These pieces, which are likely very hard and sharp, might damage other parts of the bore, especially if embedded in the bullet. So, barrel erosion is due to the interaction of heat, pressure, friction, and chemistry. More material is exposed to the cycle.

    If you go to the Lilja website, he writes a bit about bore erosion. Interesting to me that he rates the .25-06 right alongside the .308 Win. Keep in mind that his definition of accuracy is based on competition.

    Lilja also links three government studies on bore erosion submitted by a Sylvain Benoit. Most of the above is summarized from these papers, especially the Australian study, combined with my understanding from a previous life as a materials engineer and past readings on the topic. I am not taking the time to highlight what is from the papers and what is from my past so I’d suggest reading the papers and not quoting the above. I am not an expert, just an interested party interpreting and extrapolating some studies and interjecting my opinions to try to shed some light on the topic. Keep in mind that these are military studies – the powders they used are not the same as we use. Some are for big guns.

    Consider this a starting point. Perhaps you know more and might contradict some of this. If so, my ears are always open.

    Also, a couple of these papers discuss chrome and other surface treatments. I would be very interested to see if the ceramic Ultra Coating technology mentioned elsewhere by Beekeeper tends to reduce barrel erosion over the long term.

    So in real life? I think that recommending a cool down between short strings is wise advise. Even with nonstop shooting substantial erosion might take hundreds of rounds. It might not. Barrels are unique. Accuracy will probably suffer with bore erosion, but that might mean going from 0.25” groups to 0.50” groups, or 0.50” groups to 1.00” groups. Some of us might not even notice. I guess it is up to the individual shooter to determine when his barrel is shot out.

    Here are the Lilja links.

    http://www.riflebarrels.com/faq_lilja_rifle_barrels.htm
    http://www.riflebarrels.com/articles/barrel_life3.pdf
    http://www.riflebarrels.com/articles/barrel_life2.pdf
    http://www.riflebarrels.com/articles/barrel_life1.pdf

    Leave a comment:


  • hunt_fish_sleep
    replied
    High velocity bullets like the .220 swift are moving so fast that the rifling cannot always effectively engage the bullet and the bullet may slip a little from the grip of the lands. After several thousand shots, your barrel will become what is known as dethroated, which is the wearing away of rifling.

    Leave a comment:


  • bonnier-admin_2
    replied
    O”BROTHER!!!

    LOL!

    I’m going to wait until noonish tomorrow to answer the question.


    Some of you are right, but half right!!

    Leave a comment:


  • shane
    replied
    I would like to see more progressive twist testing on rifle barrels. Could work out nicely.

    Stainless barrels last a little longer, as do chrome lined barrels. Any cartridge spitting bullets near or at 4000 fps qualifies as a "barrel burner".

    Leave a comment:


  • CPT BRAD
    replied
    Ed J throats wear out the fastest because the bullet goes from 0 spin to full spinning (running with the lands and groves) within the first couple of inches of the chamber. It is nearly ripping the copper from the bullets (and indeed will if you either shoot too light a bullet or shoot the bullet too fast) and is very stressful on the steel. Also frictional force plus the hottest part of the ignition process is greatest right there, this heats the steel allowing it to wear at a faster rate than at the muzzle where you are dealing with a fully spinning bullet and less compressed gas.

    What I don't know or understand is why the rifle makers don't put a progressive spin barrel on it like Smith and Wesson does on the XVR Pistol line. Seems like the throat would last longer and if S&W can do it in 8 inches then a rifle should be able to do it in 18-22. What do you guys think? Think it would extend barrel life or benifit these little rifles?

    Leave a comment:


  • DakotaMan
    replied
    Beekeeper... I know it sounds far fetched... it did to me too. All I can imagine is the the barrel got a little spin on the one in the AM but was woefully lacking in rifling (plus I might have had a great deal of luck hitting the coyote... that happens once in a while). The key point is that the rifle actually shot well enough to hunt right up until a quick end. In another incident, I had an older but serviceable 25-06 barrel that I shot 60 grain bullets through for a test... about 100 consecutive shots at well over 4,000 fps. At the end of the test, the barrel had no rifling and I had to throw it away... no more 60 grain 25-06 tests.

    Leave a comment:

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