This often-cited and popular misconception doesn't jibe with certain facts of gas physics.
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<br>(a) The molecules of the expanding powder gas ricochet off each other (and the case wall) at about 1,400 ft/sec. NOTHING is going to hold them back, once the bullet gives way before them and starts moving.
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<br>(b) The gas is EXPANDING under increasing pressure, not flowing at an unchanging low pressure like pipeline gas.
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<br>Some of the popular misconceptions about the "flow" of powder gas through the neck of the case may be true ONLY if the neck constriction were significantly smaller than a much larger bore ahead of it -- but this isn't the situation in a chambered cartridge. The gas forced through the constriction of the neck STAYS constricted as far as diameter is concerned. At any given instant, the gas behind the moving bullet is exerting exactly the same pressure upon all surfaces of its confining vessels (case and barrel). That pressure increases, then decreases, from instant to instant, of course, but it's never x in one place while it's x minus y or x plus y in another place.
