Bulged Barrel?

Discussion in 'Technical Questions & Information' started by ryan42, Sep 25, 2012.

  1. Jim K

    Jim K New Member

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    The actual cause of a bulged barrel is often misunderstood. It is heat. When the bullet begins to move, it rapidly picks up a lot of kinetic energy. When the bullet is stopped abruptly, that energy is dumped in the form of heat. That heat softens the steel of the barrel and the normal pressure bulges or breaks the softened steel.

    If the bullet is not stopped, or slows to a stop, the energy dump is not as abrupt and the heat has a chance to dissipate. That is the case with a soft material in the barrel (peanut butter?) or with something like rainwater, which does not slow the bullet significantly. But if the front bullet is at the rear, so the second bullet is touching it, the second will not be stopped, and the two bullets will exit as one, at effectively double the mass. The pressure will be higher than normal, but the the barrel will not bulge.

    Also, if a bullet is stuck in the barrel and a round without a bullet is fired, the powder gas alone does not have enough kinetic energy and is not stopped abruptly enough to cause a bulge. In fact (dirty little gunsmith secret) a common way of removing barrel obstructions like broken bore snakes is to use a half charge of powder without a bullet and simply shoot them out.

    Jim
  2. dcriner

    dcriner Member

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    Jim, I'm trying to reconcile that versus a muzzleloader with the ball not rammed tight against the powder charge, leaving a vacant space behind the ball. Supposedly, that will increase the pressure and somehow damage the bbl.
  3. CCHolderinMaine

    CCHolderinMaine Well-Known Member

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    Also, if a bullet is stuck in the barrel and a round without a bullet is fired, the powder gas alone does not have enough kinetic energy and is not stopped abruptly enough to cause a bulge. In fact (dirty little gunsmith secret) a common way of removing barrel obstructions like broken bore snakes is to use a half charge of powder without a bullet and simply shoot them out.

    Thank you for that answer, that's a question I've wondered. So what you're saying is; even if I cemented shut the end of a barrel with something completely immovable, even if I fired a full normal powder charge(no projectile), the barrel should not be damaged.
  4. jaydub

    jaydub Former Guest

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    All my Glocks have after market barrels. I highly recommend this as the way to go.
  5. Jim K

    Jim K New Member

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    Hi, dcriner. I have heard that time and again, but I tried it and nothing happened except the bullet blew out. I have even challenged one fellow to prove to me that it can happen and offered to pay for the rifle if the barrel burst or bulged. He refused, but kept insisting that he read that someone said that maybe it happened to a cousin.... You get the picture.

    Hi, CC holder. Well I have never tried cementing the barrel shut, but I think the answer would be that with no bullet the plug would just be blown out. Now if a bullet were fired, the precursor wave would probably blow out the plug. But if it didn't, and the bullet stopped, the muzzle would be opened up the same as when a rifle is fired with mud in the barrel. Those kinds of obstructions usually result in the barrel splitting along the fault lines (that is the rifling) and the barrel opens up in a nice flower pattern.

    Of course, you made your plug immovable. What would happen is just that the pressure would build up as the powder burned. If the barrel were weak, it could burst, but with a normal barrel that gas would be contained. The pressure would be lower than normal chamber pressure since the gas would have much more room for expansion than in just the chamber.

    Jim
    Last edited: Sep 27, 2012
  6. targetacqmgt

    targetacqmgt New Member

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    Umm what kind of oil-thick viscosity? I know about using a liight coat of oil-but never heard of oil as obstruction. Cosmoline yes:eek:
  7. CCHolderinMaine

    CCHolderinMaine Well-Known Member

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    I guess you've finally helped me boil my question down. Is the barrel capable of withstanding the same pressures as the chamber is? Is the chamber stronger in any way that the barrel?
  8. ryan42

    ryan42 New Member

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    Now that you said that im going to take the rest of the bullets apart to make sure there is no double charge thanks for mentioning it.Know matter how much one thinks he knows about guns its amazing how much we dont know.:)
  9. dcriner

    dcriner Member

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    If a little extra Rem Oil swabbed in the bore can cause a barrel to bulge, or worse, think about a muzzleloading musket rifle loaded with a Minie ball, gooped up with grease in its grooves and base.
  10. JLA

    JLA Well-Known Member

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    Excess Oil CAN cause barrel damage. Thats why it says in the owners manual for your firearms to not leave excessive lubricant in the bore if you are going to shoot it. Obviously thinner, less viscous oils wont pose as much of a threat as they are more likely to just get pushed out ahead of the bullet. but it can happen ere regardless.
  11. Jim K

    Jim K New Member

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    Hi, CCholder. No, but it doesn't have to. The highest pressure is in the chamber and right in front of it, which is why barrels are made thicker in that area. In normal firing, as the powder burns and the bullet moves up the barrel, the pressure decreases. IIRC, the port pressure (an inch from the muzzle) in an M1 rifle is only about 2000 psi. If it were still 50,000 psi, the op rod would be very unhappy.

    The same is true even more so without a bullet. Contrary to what is sometimes believed, few obstructions provide anywhere near the resistance of a normal bullet. Without that resistance and confinement, the powder burns poorly. The gas expands but acts like it is in a long cartridge case, so the pressure is a lot lower than in normal firing, and often the case is not even obturated, that is, the pressure is too low to expand the case neck to seal it and the case is heavily sooted. (In an excess of caution, I never use a full charge in shooting out an obstruction; 1/3 will usually do fine, with a cotton filler.)

    Jim
    Last edited: Sep 27, 2012
  12. targetacqmgt

    targetacqmgt New Member

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    good point - oil it for storage, swab it out before firing??
  13. JLA

    JLA Well-Known Member

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    Exactly
  14. Jim K

    Jim K New Member

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    On the oil in the bore business, I would have to ask what is considered excessive. A barrel plugged with hard grease could be a problem, the same as a barrel plugged with mud. But I can't see how the thin coating of oil normally used to protect a barrel in storage would be enough of an "obstruction" to cause a barrel to bulge or burst. Of course, it could cause the first shot to go somewhere other than where the rifle is sighted, but that is not the same thing as barrel damage.

    Jim
  15. binlookin

    binlookin New Member

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    Re: Glock Bulged Barrel? I decided to chime in here, Because 'See Below"

    Glock Pistols have an "UN-SUPPORTED" chamber and are not intended to fire RELOADS. If you want to shoot reloaded ammo in your glock, then have a aftermarket barrel fitted for it. Be thankful that it jammed and you could not chamber another round, you were very fortunate.
    More info. on this "BULGED BARREL" with the Glock can be found on:
    castboolits.com .

    {The reason I know this! Last week I started to research information on reloading for the Glock 40 S&W [duty issue] for my 'Almost half addopted Step-child' who now works part time for the local Court system as a bailif, deputy, probation/community service armed escort [aka chain gang guard].
    On his pay and WITH a young family he finds it 'tight' to shoot enough to keep in good practice. He had asked me to reload for his 40S&W. Since I had never fired a 'Glock' or the 40S&W, I went looking and the above is what I found!
    He will now practice with one of my 1911's or my S&W 9mm.
    PLEASE NOTE: I am not in any way harping on the 'Glock' firearm, from what I know of them? They are one of the finest semi-auto pistols in use today! However as with any firearm, if you are going to use reloaded ammo. first do your homework and keep it safe.
    binlookin.
    Last edited: Oct 4, 2012
  16. Jim K

    Jim K New Member

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    Glocks do not have an "unsupported chamber". In the Glock, the cartridge is not as well supported at the lower rear than with some other guns, and that has reportedly caused problems with some ammunition, both reloads and factory ammo.

    But there is no, let me repeat, NO, indication that proper reloads are going to blow up a Glock or any other gun. Of course, reloads that have excessive powder charges or that use defective or excessively worked cases can be a problem in any gun, but the blanket statement that reloads will damage a Glock is simply not true.

    As I said before, ALL gun makers advise against use of reloads for the simple reason that they can't and won't assume any liability for their gun if used with ammunition of unknown origin and unknown loadings.

    Jim
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