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Cake day: July 8th, 2023

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  • The standard “ball” bullet used by the Russian military, at least, in the 5.45x39mm is designed to easily tumble once it is inside the target. It is more of an effect of the bullet’s construction and fine tuning of the rifling twist rate than the caliber itself. But it is still supposed to remain stable with the nose pointed forward when traveling to the target. Otherwise it becomes extremely inaccurate and loses its velocity very rapidly, which causes it to fall short.


  • It is keyholing. It happens when as you can see the bullet loses stability and tumbles in the air before hitting the paper sideways. It can be caused by many things. Insufficient rifling twist for the length of the bullet being used is one of them. The bullet hitting the ground or something else before hitting the target is another possibility.

    Either way, it isn’t a desirable thing and indicates that something is wrong. The fact that the PLA members are proudly posting pictures of a bunch of keyholes randomly splattered all over a target like that suggests that they think this is normal and that therefore they don’t know what they’re doing.

    The term “keyholing” is also sometimes erroneously used to refer to when two bullet holes are touching on paper.


  • DaddleDew@lemmy.worldtoScience Memes@mander.xyzWhales
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    1 day ago

    As sound travels through a water layer where the speed through which it travels varies with depth, the sound will tend to refract towards where it is the slowest.

    A layer where temperature decreases as depth increases will refract sound downwards. A layer that has the inverse temperature properties will do the opposite. A layer that is isothermal (where the temperature remains constant as depth changes), will still tend to refract sound upwards because the increase in pressure also increases velocity, although not as strongly as temperature does, which is why temperature differences can easily overcome this effect where the water is not isothermal.

    If you have a layer that refracts sound downwards on top of a layer that refracts sound upwards, you just created a sound channel, which acts as a wave guide in which sound will remain trapped and travel far longer distances horizontally before dissipating.

    Ultimately you can’t really put a number on the required temperature differences because there are many other factors to take into account like how steeply the speed of sound changes, how tall the layer(s) are, what is the frequency of the sound, or how much of it you want to remain “trapped” in the sound channel.



  • My grandfather did the exact same thing. But he was in conquered France and did it to avoid being drafted by the Nazis.

    Edit: There were also a stories of other people in the village finding other ways to avoid the Nazi draft. One of them pretended to be deaf and managed to avoid falling for a few tricks the Germans played on him in an attempt to expose him, such as dropping a coin behind his back. Another one reported to the draft medical examination after purposefully biking over an insanely long distance. When he arrived he was completely exhausted and the doctor deemed him too anemic for military service. All of those in the village who couldn’t dodge the draft were sent as cannon fodder on the eastern front and never returned, except for one “lucky” individual who lost a leg.










  • I’ve spent over a decade in the army where you’re taught to pride yourself into “embracing the suck” and the whole “pain is all in your head” mentality. I have now taken a different career path and realized that this kind of mentality is only useful in very specific cases and is otherwise very bad. But to this day I still tend to downplay and hide my problems/pain whenever things are wrong.

    That nearly got me killed a year ago when I showed up at the ER with pulmonary embolism (likely caused by a COVID infection) and the doctor dismissed it because I didn’t look in pain enough for it to be that. The doctor sent me home untreated. It would have likely killed me had I not returned the day after to see another doctor who luckily took me seriously and got me a CT scan that revealed the problem.