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Gun physics question?

Discussion in 'Handloading and Reloading' started by jski, Jul 14, 2017.

  1. Walkalong

    Walkalong Moderator

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    I answered that one in the other thread. :)
     
  2. hdwhit

    hdwhit Member

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    No, not at all.

    Can crimping a bullet in place or using a heavier bullet with the same powder charge increase chamber pressure? Yes. But, published maximum loads for the 30 M1 Carbine - including those using H110 - are already close to the SAAMI maximum of 40,000 psi for the cartridge, so doing something to intentionally increase that pressure in the name of a few extra FPS is really nothing short of madness.

    As an academic exercise, could you take the 30 Carbine cartridge, strengthen the case and put it into an action proofed for 50,000 or 60,000 psi, crimp it, load a heavier bullet and get "more" from it; certainly. But it would no longer be a 30 Carbine cartridge.
     
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  3. murf

    murf Member

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    i beg to differ here. a heavier bullet will have a longer shank and more surface area contacting the case, which will increase the neck tension. this is one reason why heavier bullets use less of a given powder than a lighter counterpart.

    murf
     
  4. murf

    murf Member

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    that is why we use reloading manuals and not educated guesses.

    murf
     
  5. Elkins45

    Elkins45 Member

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    Making the bullet heavier to increase inertia cuts both ways: you also increase the likelihood that recoil will pull the case off the bullet, locking up the action.
     
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  6. jski

    jski Member

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    Elkins45, an interesting point.
     
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  7. Walkalong

    Walkalong Moderator

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    The tension, or how hard the case is squeezing the bullet, remains the same, but it has more to grab, but also has more to hold under recoil. It would take a math major to figure it out. :)
     
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  8. Blue68f100

    Blue68f100 Member

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    Well it has the same surface area holding the bullet even though its set deeper. The difference is getting the mass started moving. Once the mass is started the friction is the same provide the jacket/core is the same.
     
  9. X-Ring

    X-Ring Member

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    I don’t understand why you need to get more out of a cartridge, any cartridge, than it was designed to give. Many things can be done to increase the pressure, most of them are not wise. If you need more performance use a different cartridge.
     
  10. Rule3

    Rule3 Member

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    There is never an Engineer around when you need one!:)
     
  11. mavracer

    mavracer Member

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    Yes but the difference in velocity from a heavy crimp is minute.
     
  12. Varminterror

    Varminterror Member

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    This isn't true either. Heavier bullets, given similar profiles, have longer shanks, in other words, larger bearing surfaces between the bullet and the bore. The friction is proportionate to the contact area - and longer bullets, aka heavier bullets, have more contact area, hence more friction.
     
  13. Jenrick

    Jenrick Member

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    Also don't forget that in a given chamber, you can only make a bullet so long. Any additional bullet length goes back into the case, this can lead to higher pressures, but past a certain point it will decrease the possible amount of powder thus decreasing velocity.

    -Jenrick
     
  14. Archie

    Archie Member

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    Yes, let him smith if he provides the services you want. Remember this; just because he's a gunsmith, even a good one, does not know he knows much about interior ballistics. Some do, some don't. Let's not start campfire stories...

    Gunsmith says,
    This is ALMOST correct. With the bullet slightly retarded from leaving the case, burn will be more complete and uniform. Crimp, or 'more' crimp is one method. So is loading (usually a rifle) bullet into the leade. So is sizing the neck down smaller to create a tight 'grip' on the bullet. So will some form of sealant. (I recommend against Super Glue.)

    Not really.

    Yes, a heavier bullet will retard bullet movement and cause a more uniform and complete burn. However, with the same powder charge, the heavier bullet will not be launched as fast (muzzle velocity). Not to mention the powder charge may be an overload with the heavier bullet. The 'standard' weight .30 Carbine bullet is 110 grains. The next heavier bullet weight (quick look) is 125 grains. But it may be too long to load without the tip of the bullet protruding out the face of the cylinder. (Maybe it will fit, but I'd bet 180 grain bullets or so won't; there's a limit.) Obviously not a solution. One could load the heavier bullet deeper into the case, but this means reducing the 'chamber' area, requiring a lesser powder charge.

    Face it; the cartridge has limits - as do all - and one is limited by the mechanics of the instrument, the physics of the cartridge firing and so on. Not to mention a Blackhawk barrel is shorter than an M1 Carbine barrel.

    Don't worry about "...not getting all you can...", you probably are. Wear earmuffs (those suckers are LOUD) and enjoy.

    I forgot to mention something you said. About a bullet doing 1200 fps leaving the barrel in (so much time)... The bullet is stationary at the chamber end and moving 1200 fps exiting the muzzle. So the average velocity of the bullet - and transit time is based on 'average time' - is 600 fps. But all the powder in any firearm is consumed within the first few inches of barrel travel.

    Yes, some powder isn't burnt. However, it wouldn't be burnt if one had a six foot barrel. And the muzzle flash is NOT unburnt powder.
     
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  15. armarsh

    armarsh Member

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    Not sure about your prose, but you are right.
     
  16. murf

    murf Member

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    powder burn rate increases with pressure, so, please, use a reloading manual and stay within its bounds. trying to linearly extrapolate load data will get you hurt.

    murf
     
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  17. jski

    jski Member

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    Archie, for umpteen years I've been told that the reason the .30 Carbine Blackhawk has such a loud report and blazing flash is unburned powder burning when the bullet exits the barrel. Even though my .357 has just as loud a report and blazing a flash.
     
  18. Walkalong

    Walkalong Moderator

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    95% or better of muzzle flash is from the combustion products of the burned powder reacting with the oxygen in the air.

    https://www.thehighroad.org/index.php?threads/muzzle-flash.426738/

    https://www.thehighroad.org/index.p...for-reduced-muzzle-flash.639073/#post-7901355

    https://www.thehighroad.org/index.php?threads/noob-question-re-flash-power.443140/#post-5519267
     
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  19. murf

    murf Member

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    if that were so, only the outside edge of the gas envelope would show color. the gasses inside the envelope don't get exposed to the atmosphere right away.

    the muzzle flash is a temperature thing, like heating a piece of steel to cherry red, then orange, then yellow, then, finally, white. gasses work the same. the muzzle flash is hot gas which cools off real fast (thus loosing the color) a short distance from the barrel. watch a campfire flame change colors the farther it gets from the wood ... then disappear.

    murf
     
  20. Walkalong

    Walkalong Moderator

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    There just isn't that much unburned power left. It's flame from powder, but not unburned powder.
     
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  21. GooseGestapo

    GooseGestapo Member

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    It's actually unreacted oxidizer. Gunpowder isn't a stoichemetrically balanced material. Because of the sealed system, it requires its own released oxygen to provide the oxidizer for the combustion. Though the powder has typically burned within the first 3-4", the uncombined oxidizer will flash when exposed to the air. There is also the 256/1 expansion of the combustion and the release of pressure to the air. Also, the .30Carbine bullet is supersonic.

    Neck tension on the .30Carbine is more critical than the crimp. Die tolerances and case neck thickness are all over the place. Also, the Carbine isn't a straight case. It's tapered, similar to the 9mmPara. Headspace can be regulated by die setting. Revolvers chambers tend to be less sloppy than Carbines. But don't get to tight with the semi autos. They can slamfire a high primer.
     
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