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Can irregularities in a bullet jacket harm a rifle barrel?

Discussion in 'Rifle Country' started by FireInCairo, Mar 13, 2013.

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  1. briansmithwins

    briansmithwins Member

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    Surprised you didn't move the barrel back and rechamber.

    Not that gas operated barrels can be rescued that way.

    BSW
     
  2. Trent

    Trent Resident Wiseguy

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    I always wanted a Krieger, this was as good excuse as any. :)
     
  3. Swampman

    Swampman Old Fart

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    I'm not sure what you expect the condition of the bores on a couple of surplus rifles to prove other than the obvious fact that shooting a rifle tends to wear out its barrel.

    While an ex G3 barrel may well have fired a good bit of copper washed steel jacketed ammo (along with cupronickel jacketed), a Yugoslavian SKS is unlikely to have fired much of anything but M-67 ball. If you're unfamiliar with this ammunition, it's just about the only affordable 7.62x39 that'll pass the "magnet test" because there's not a bit of steel or nickel anywhere in it.
    A worn out bore on a Yugo SKS seems like just about the worst possible example of why not to shoot steel jacketed ammunition.

    I'll say it again, if coated steel jackets in and of themselves were that damaging, the US military would specify gilding metal jackets for M-80 ball. They don't. The only way to tell what kind of jackets a particular box or belt of M-80 ball has is to use a magnet.

    The only way that I could really be convinced that the jackets are what's causing the problem is if the bullets were loaded in identical cases, with identical powder and primers. When you contract with Russian or Ukrainian factories and have them competing with one another to make the lowest cost ammunition, it's conceivable that a lot of corners might be cut. More erosive primers, hotter burning powders, even little things like LOOSE SCRAPED OFF PIECES OF BULLET JACKET around the bullet/case juncture (I think I read about that somewhere...) could have a detrimental effect on barrel life completely aside from bullet jacket material.

    I've dug many steel jacketed M-80 ball slugs out of various berms and even after penetrating a foot or more into the ground the jackets still look pretty much like gilding metal jackets. If the plating is what's actually contacting the bore and the steel beneath it has been annealed to an appropriate level of hardness, why would copper washed jackets wear out the bore any faster than gilding metal?

    Whether its a .22 Short or a .177x.50 BMG Ultraeargeshsplitzenloudenboomer, every time you shoot a firearm you are causing wear and reducing the lifespan of the weapon, it's just a question of how much. Your guns will last much longer if you dip them in hot cosmoline, wrap 'em in grease paper and then store them in a temperature and humidity controlled warehouse.
    Unfortunately, it won't do squat for your marksmanship.

    My apologies, I am, in fact, aware that that not all rifles are AR-15's, but it is my understanding that the S&W, M&P (the weapon that the OP owns and expressed concern about in the first post of this thread) IS such a weapon.

    H&K 91's and SKS's (at least those with threaded barrels like your Yugo) are not that difficult to rebarrel, a good Gunsmith can do the job quite easily. In fact AIM Surplus has new, in the white 59/66 barrels for only $55.

    I have an old 1962 Winchester Model 100 in .308 that according to Winchester, is impossible to rebarrel. While I don't shoot it a lot, I do keep it sighted in (sometimes with steel jacket M-80) and hunt with it occasionally, even though I know that doing so will undoubtedly shorten its useful life.

    To me it's a tool, not a museum piece.
     
  4. stubbicatt

    stubbicatt Member

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    Based on the foregoing, I have concluded:
    1. Barrels are wear items which will need replacement.
    2. The factors that contribute to barrel wear are:
    a. Jacket material
    b. Nature of the priming compound, whether glass or other aluminum powder is included.
    c. Nature of the powder, whether corrosive or not, whether stick powder or ball powder, temperature of powder burn.
    d. Quantity of powder burned, i.e. after 8 pounds of powder have gone down the bore, it is worn out.
    e. Nature of cleaning regimen, i.e., do you use a good coated cleaning rod and clean from the breach?
    f. Presence of rusting, i.e. was the bore cleaned and properly preserved after cleaning.

    g. Overbore ratio, and angle of case shoulder? --I have read that seriously overbore cartridges will erode the throat more quickly as will those whose shoulder angles converge on the case mouth, thus funneling and directing the hot powder gasses to that spot on the throat of the rifle chamber....

    Of all of these, the only one you cannot control (other than to not shoot the rifle) is the amount of powder thru the barrel, am I right?
     
  5. Trent

    Trent Resident Wiseguy

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    Anecdotal evidence is just that; I'm giving my personal experiences, nothing more. :)

    The US military is a horrible example to provide for whether or not to shoot M80 ball. They really, really don't care about what projectiles they send down the bore (whether it be depleted uranium or lead ball) as long as the munitions meet military specifications. Why? Because they monitor the serviceability of barrels and toss them out like so much scrap metal when they are used up. They happen to have an enormous budget for defense (last I checked, they were spending a great deal of my tax money...)

    Heck, if you want to go down the road of detrimental effects of barrel life, let's throw improper cleaning in to the mix. When I had my gun shop I saw FAR more barrels with crowns damaged due to Bubba's improper bore cleaning, or dark bore mil-surp pieces, than I ever saw of shot-out specimens.

    Will loose, scraped off pieces of bullet jacket affect barrel life? Not very damn likely. Will they contribute to excessive fouling? Most certainly! If the person doesn't know how to properly clean the rifle, they might assume the bore has been damaged after this affects accuracy... or (more likely) might even damage a perfectly good bore themselves, while giving it a Bubba Scrub.

    How thick is the groove-to-bore relationship, compared to the thickness of the copper wash? I would bet that in MOST instances the rifling is etching the bullets WELL past the softer metal and in to the steel jacket. (Even after the rifling starts to wear, the bullet will begin "tilting" slightly as it goes down the barrel, continuing to etch as deep as it can, wearing the barrel further.)

    In the study posted earlier we saw that in as few as 5,000 shots, bimetal ammo completely wore out the rifling of the chrome-molybdnum-vanadium bushmaster barrels. A normal (non-chrome) steel barrel will go even faster than that.

    An AR involves hand tools, and really, no special skills.

    Other guns require finding someone capable (not always easy to do), shipping it off, and spending as much or more on labor as you spend on the barrel.

    Swapping an H&K 91 or G3 barrel is no small task. Requires custom hydraulic jigs to get the barrel pressed out. (Not to mention precise alignment on the re-fit, drilling in to the barrel to time the cross pin, etc.)

    An SKS is quite a lot easier, but usually requires receiver modifications (facing the front of the receiver) to get the barrel ejector port relief cut timed properly to the receiver.

    Some of us own pieces that would be at home in a museum, and actually DO shoot them sometimes. I own several firearms which are rare, to the point the National Firearms Museum doesn't have a specimen. :D

    While I agree with you that - yes - barrels are wear items, the degree of difficulty in replacing some vs. others varies widely, as does availability of replacement parts. Some of my guns were designed to quickly replace the barrel (most of my belt guns were designed for it; but FINDING barrels for some of them is about impossible - try finding a DShK barrel.). Others? It's a stone cold pain in the butt. (RPD comes to mind).

    In an AR-15 it's not a big deal, 15 minutes, a punch for the gas tube roll pin, and a barrel wrench is about all you need.

    But ... not all rifles are AR-15's... and what you feed through them DOES matter on barrel life. I wouldn't shoot very much bimetal through my SCAR. Sure, it's damn easy to swap the barrel. But not cheap; costs $1200+ for a new assembly.

    One other thing to consider... Eventually, as ammo prices come back down, people who sold all of the bimetal stuff at 2x+ the normal going price, can buy an equal amount of good ammo. :)
     
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