JSB Knock Outs 10gr .177 |
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Pauly5
Forum Moderator Joined: 10 Mar 2013 Location: Titahi Bay Status: Offline Posts: 1409 |
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I could be wrong, but isn't any object that goes faster than sound going to create the "crack"?
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kruzaroad
Senior Member Joined: 02 Jul 2022 Location: Hastings 4 now Status: Offline Posts: 2282 |
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The speed of sound in feet per second (fps) depends on the temperature and the material through which it travels:
At 0° C (32° F): The speed of sound is 1,086.9 ft/s. At 20° C (68° F): The speed of sound is 1,130 ft/s. At room temperature: The speed of sound is 1,125 ft/s. The speed of sound is faster in warm air and slower in cold air. The speed of sound in water at 8° C (46° F) is about 4,721 ft/s. Transonic is the level that both sub and super sonlc airflow start to form on different parts of the projectile,the projectile shape plays a part in that formation. It affects any projectile. It happens mostly when dropping to out of supersonic but if your right up on the edge of that speed,airflow differences created by the slug can induce the effect. Most of the stuff I've looked at has shooters around 950fps max if they want to say under transonic. As you can see temp could effect that margin. Look at speed of sound in water. At least that's my understanding of it. |
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RangerPete
Senior Member Joined: 18 Apr 2023 Location: Cambridge. Status: Offline Posts: 884 |
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The “crack” is called a sonic boom and happens when an object breaks through the sound barrier, I.e. goes faster than the speed of sound (on that day, at that altitude, at that temp etc…)
As Kruza says above, speed of sound is dependent on the density of air (or other medium) it is traveling through, hence the altitude and temperature dependency. But as a general rule of thumb on most average shooting days, in most average shooting countries, it is between 1100 and 1150fps. All the top guys who are shooting slugs in extreme long range and bench rest competitions shoot slugs between 950 and 1100 fps and you never hear any sonic booms when they are shooting. As far as transsonic pressure waves effecting projectile stability goes, all those top guys are shooting sub moa groups at 100, 120, 150 even 200 yards. So transsonic speeds don’t seem to be effecting their slug performance in any way. |
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Walk quietly, but carry a big stick.
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kruzaroad
Senior Member Joined: 02 Jul 2022 Location: Hastings 4 now Status: Offline Posts: 2282 |
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The Guinness world record, .177 for distance is sub 12 foot pounds with the 7.33 gr pellet at 850 fps!
This from the guy who has done the world's furtherest shot. Big bore 1265m, 1777 yards (Quote) thank you, with this I want to take a longer break from shooting above 1200m. It was for a velocity of 260 m/s = 853 fps, at a higher velocity the BC would be slightly higher. My friend from abroad who also uses ATP Smooth 49.5gr but at higher speed measured BC G1 0.238 at speeds of 294 m/s 964 fps ( end quote) Think you better look at what fps the guns were set to not the fps they can produce. To because all of the Dr top guys aren't shooting over 1000fps Here's a 🔗 to video. Go to very end even then you'll here them say “maybe 900fps“ https://youtu.be/FQW3x8EqZi0?si=QIhfqRaXMI6hJoca Edited by kruzaroad - 14 Oct 2024 at 10:58am |
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kruzaroad
Senior Member Joined: 02 Jul 2022 Location: Hastings 4 now Status: Offline Posts: 2282 |
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What is an average shooting country?
That's got to be the biggest load of cat trap I've ever heard. India has a strong air rifle following high arse temps. Canada had a strong air rifle following they hit sub zero. Asian areas can be hot and have a near 100% humidity that affects flight etc etc |
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RangerPete
Senior Member Joined: 18 Apr 2023 Location: Cambridge. Status: Offline Posts: 884 |
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Average shooting country is not the south pole and not the saraha desert. Average shooting country is where most people like to live because the average temperature is above freezing and below 50
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Walk quietly, but carry a big stick.
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kruzaroad
Senior Member Joined: 02 Jul 2022 Location: Hastings 4 now Status: Offline Posts: 2282 |
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That makes no sense either. Every country contains multiple environments. I've shot in the snow. Wet.wind.high humidity.low humidity.rain.sun.crisp nights warmnights. there is no average shooting conditions countys it in my view.
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RangerPete
Senior Member Joined: 18 Apr 2023 Location: Cambridge. Status: Offline Posts: 884 |
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I hate dissecting birds.
Feathers are such a pain in the ass, and they go everywhere. Was doing a culling job yesterday morning and while I was wondering around looking for my target species, a few pigeons came down and landed in the paddock. The land owner had said if I can I should shoot them too, so I sent a few 13grain knock out slugs their way. Got 5 or 6 and then got busy with other stuff. One in particular was a very pretty white, grey and black bird, would have made any pigeon fanciers heart happy, but anyway, it turned and walked directly towards me and took a slug into the dead center of its chest, just below the neck. I though if these 13grainers expand like the 10grainers, that one had the best chance of stopping in the bird with a head on chest shot, so I collected it and brought it home. After 12 minutes of careful dissection, following the wound channel basically along the full length of the bird just under the spine, and trying to keep all the feathers on the bird and not all over my yard... I found a small exit hole, hidden by feather, just above the tail feathers So I'm still none the wiser to how they perform. More investigating to come. |
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Walk quietly, but carry a big stick.
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kruzaroad
Senior Member Joined: 02 Jul 2022 Location: Hastings 4 now Status: Offline Posts: 2282 |
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You could skin it. It would keep all the feathers still anchored in the skin and exit holes show up better on the meat.
So what was the wound channel like? Did it look like it expanded? |
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RangerPete
Senior Member Joined: 18 Apr 2023 Location: Cambridge. Status: Offline Posts: 884 |
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Wound channel had a lot of damage all the way through, and plenty of congealed blood. More damage than I would expect from an 8.44gr exact. The exit “hole” if u could call it that also looked bigger than what I would expect an 8.44gr would make, so I’m guessing it wasn’t just the extra FPE and there was some expansion.
More tests will reveal all. |
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Walk quietly, but carry a big stick.
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